Twitter has acquired two other companies so far, that we know of. Search engine and sentiment analysis service Summize became Twitter's own search engine and Values of N sold its assets so engineer Rael Dornfest could be brought into the company. Here are ten other startups we think that Twitter should consider acquiring next. Which kind of company would you most like to see become part of Twitter itself? We've got a poll below.

Some of these we think are likely acquisitions, some less so. In making this list we considered both functionality that would be helpful to have added to Twitter's own site and technology that would be worth buying instead of just building in-house. Whenever a platform company builds technology that a number of other startups offer, there is a risk of scaring other people away from investing in development that the platform could just reproduce. Acquisitions of startups on a platform probably increase the appeal of development though, as it's a chance to get in on the game.

Quite Likely, if It Hasn't Happened Already

Bit.ly is the most full-featured and popular URL shortener on the market right now and was recently selected as Twitter's own shortener of choice, dethroning TinyURL. Bit.ly offers all kinds of smart analytics, from real-time click tracking to semantic analysis of topic keywords from the links that people tweet.

One trusted industry source speaking on the condition of anonymity told us that Bit.ly servers "were moved into Twitter's racks months ago in preparation for this change" [of becoming the default shortener]. Bit.ly is becoming too important to Twitter to keep that functionality outside the company's own shop and the two companies share some investors. We will not be surprised at all if a Bit.ly acquisition by Twitter is announced sometime in the near future.

Could Happen...

Tweetmeme is another fast growing Twitter analytics service that tracks sharing on the service. With another chunk of new features just added today, the service is looking a whole lot like "Feedburner for Twitter" but with even more viral distribution possibilities. The Tweetmeme API is quite interesting and could complement Bit.ly quite well.

Twitpic is a popular way to share images on Twitter. The site faces a strong challenge from ImageShack's YFrog, but independent Twitpic would be a cheaper acquisition and is already well known among Twitter users. (Twitter should probably look at Enjoysthin.gs; it's got the best user experience.) An increase in imagery on Twitter would probably offer the company a lot more advertising real-estate.

Tweepz is a fascinating Twitter search engine that acts like a directory that lets you parse your results using various metrics gleaned from Twitter. Check out this search, for example. Twitter could benefit from making this kind of search available to users, advertisers and researchers - and Tweepz has already built it. See also Twazzup, another company doing interesting things with Twitter data.

Longer Shots

An iPhone app company could be a good buy for Twitter; there's certainly plenty of options. M.Twitter.com is a good mobile service already but someone specializing in super high-quality Twitter apps for the iPhone, Android and Pre could be good to bring in house. It could be AteBits, makers of Tweetie. There may not be enough reason for Twitter to buy one of these companies, though.

A desktop Twitter app company could help Twitter increase user engagement. Many of the most serious Twitter users (though not all) swear by desktop access. Twitter could acquire the most popular and arguably most innovative desktop app, Tweetdeck, or it could bring Seesmic in house. Tweetdeck would be cheap and shares investors with Twitter. Desktop apps may be too limited in appeal to be a compelling acquisition target.

Geo-location could be a good feature to add to Twitter. Search by user location could be made much more meaningful and the list of things that could be done with it is very long. Brightkite is popular and well developed, Shizzow is pretty and wouldn't be expensive. On the other hand, browsers themselves will likely all become more location aware in the near future and Twitter may be satisfied with its current location data.

A semantics company could bring structure to the Tweets, making them more useful and easier to advertise against. Right now links Tweeted are semantically analyzed by Reuters' Calais and sent to Bit.ly, but we wouldn't be surprised if Twitter was interested in scooping up a small semantics shop and helping it scale so that analysis was being done in house. Twitter may feel like semantics don't need to get that close to consumer users, though. (Disclosure, Calais is a ReadWriteWeb sponsor.)

Topify is a widely loved service that intercepts your new Twitter follower notification emails and sends you much more useful ones. It's great but probably too easy for Twitter to just reproduce itself.

FriendFeed plus Twitter would be a match made in heaven. It would be an engineering powerhouse. It would be a step towards mainstream user adoption of FriendFeed, a service that can't make up its mind which end of the sophistication spectrum it's targeting. It's also quite unlikely to happen. If there's one related startup we can imagine turning down a Twitter acquisition offer, it's probably FriendFeed. (Though the investment-laden and highly ambitious OneRiot is a close second.) Nonetheless, it would be awesome if FriendFeed's cross-network aggregation, threaded conversations, groups, media support, search and more joined forces with Twitter.

Ultimately, it may be most likely that Twitter's next acquisition will be something vapid. A service that aggregates shopping Tweets, or celebrity Tweets, or something else that will fall short of taking advantage of the Twitter platform's huge potential to change the world. Twitter staff makes relatively simple use of its own service, so hoping that it will acquire companies that make it all the more powerfully sophisticated may be an early adopter's pipe dream. [Update: After some discussion this afternoon, I am thinking it's time to reconsider this position I've held for some time. Twitter staff is not full of dummies, I'm sure, and it has probably been inappropriate of me to write as if that's the case.]

Maybe not, though. We wouldn't be shocked to see Twitter pick up at least a few of the companies above. What do you think? Are there other services you'd like to see become part of the Twitter team even more than the above? It's a wild and woolly micro-content ecosystem out there - anything could happen.

You can find ReadWriteWeb on Twitter, as well as the entire RWW Team: Marshall Kirkpatrick, Bernard Lunn, Alex Iskold, Sarah Perez, Frederic Lardinois, Doug Coleman, Jolie O'Dell, Dana Oshiro , Lidija Davis and Steven Walling.

There are lots of location based social networks available, but this one is refreshingly simple. Is that enough to effectively differentiate Shizzow? It's going to have to be, because there's not much else about the service that's unique. Most features are easily reproduced, however, and usability may be the key point of competition in this market.

Shizzow let's you "shout" about where you are, based on the name of the place instead of its address (that's figured out in the back end), and listen to the shouts of friends' locations. You can see who hangs out at particular locations and what locations your friends hang out at most often. Ultimately, the service should help your lonely self connect with people in public more often, if that's something you're looking for.

Posting can be done through a mobile interface, a Google Gadget or the Shizzow web page. There's some IM and SMS integration as well.

Is there an API? Not yet. When will it open for general availability? Just before the SXSW conference - that's pretty cliche, but it could work.

Why would you use this instead of Brightkite, Loopt, something built on top of Yahoo Fire Eagle? If you're comfortable using any of those services already, you probably have no need to use Shizzow. The company's attempts to explain how different their service is haven't been particularly convincing.

The Upside

If you're looking for a less geeky, attractive, easy to use location based network to use with a wider circle of people than just early adopters - Shizzow will likely play well with that crowd (the rest of the world). If we told you three years ago that a simple service that let you broadcast 140 characters or less about "what you're doing" was going to take the world by storm, you'd probably have called us crazy. Similarly, comparing location based social networks on features may not be the best criterion.

Usability is key to adoption beyond the relatively small number of people who obsess over every feature and Shizzow is simple, clean looking and usable. Location based social networking sometimes feels so bleeding edge pretentious that you wonder whether these communities even want more users. That's not the feeling you'll likely get looking around Shizzow.

Does the the world at large want to find friends and be found via short messages? We're not sure, but it's possible. Can Shizzow take its simple, useful tool out into the world successfully? We'll see, location based social networking is a new paradigm and given privacy concerns (even if they're not rationally "valid") it could be a hard sell to mainstream users.

Shizzow is now available for users in California. Drop by, give it a try and let us know what you think. See also WebMonkey's interview with the Shizzow CEO this morning, it's an interesting discussion about side projects, simplicity and mobile communication.