FriendFeed was co-founded by Paul Buchheit, the man who invented GMail, and by Bret Taylor, who co-founded Google Maps. They both made enough money from being early Google Employees that they never needed to work again and didn't need to sell to Facebook - but they joined Facebook because they wanted the work they'd done on FriendFeed to change the world of social networking. Here's what they bring to Facebook; it's probably going to change Facebook a lot.

FriendFeed is a very unusual social network, but we've long suspected it represents the future of social networking. We got one of the first interviews with Taylor and Buchheit eighteen months ago and that podcast is still one of the best ways to learn about how FriendFeed works.

Now that the service has been live for some time, here are the most important parts of it that will likely influence the way Facebook works.

1. Public Profiles and Content

Facebook started out as a site where you couldn't see the pages and posts of people you didn't know. It still retains a lot of that flavor, but this summer Facebook started moving toward a much more public and less private experience.

FriendFeed is very public. Everyones' profiles and postings on the site are public and the software has a very interesting flow that prompts people to discover new users that they have no connection with other than conversation around a common topic. FriendFeed's innovations in managing very public conversation will likely come in handy for Facebook as that site opens up more and more too. It's a sensitive subject, as most Facebook users like the privacy orientation just like it is, so bringing in some top minds on fast, frictionless, public social networking is a smart move by Facebook.

2. In-depth Conversations

Conversations around shared items on FriendFeed make Facebook look like MySpace. It's not that FriendFeed has more sophisticated users - though by being limited to early adopters so far is part of that. it's because of a key difference in the architecture of FriendFeed.

When I post something to FriendFeed, all of my friends see it. If one of them comments on it or "likes" it, then two things happen that don't happen on Facebook. First, our conversation suddenly appears in the news feed of all the friends of the person who commented on my item - whether they know me or not. That doesn't happen on Facebook. I can see the names of people who comment on my friends' items - but if my friends comment on items shared by their friends I don't know - there's no notification of that in my news feed.

Second, whenever anyone comments on or "likes" any item that's appeared in my stream of friends' updates - it's pushed back up to the top of my FriendFeed page. That makes it all the more likely that I will comment on it again or for the first time.

These two features lead to one thing: big, diverse, thorough conversations around items shared on FriendFeed. It's a defining quality of the service and one that Facebook users might really like to have as an option.

When FriendFeed users complain that Facebook is stupid and filled with dumb apps (remember complaining about how ugly MySpace was?) it's in large part because the conversation on FriendFeed has a lot more depth to it.

Neither of these features are as simple as described above. FriendFeed's Buchheit told us by phone today that both have a lot of complex rules that have evolved around them based on the experience of having this kind of social software in the wild. Learning what kinds of content to cross over from one social group to another and how to decay the prominence of conversations over time are among the skills that the FriendFeed team can no doubt offer Facebook.

3. Cross Group Interactions

You meet new people on FriendFeed. They show up again and again in conversations with your friends until you make some of those new people friends of your own. That's very different from Facebook, where you connect with people you already knew from real life.

4. Multiple Network Aggregation

Conversation starters on FriendFeed don't just come from people inputting text right into FriendFeed - most of it comes from content pulled automatically in from other networks. Especially Twitter. (From a technical perspective, you have to wonder if Twitter is going to turn off full "firehose" access to FriendFeed this afternoon or if they'll wait until tomorrow morning. Twitter can't be excited about giving their crown jewels to Facebook all the sudden.)

Bookmarks, slide presentations, videos favorited on YouTube - all kinds of other social networks get synced up with your FriendFeed account and then get pulled in automatically to be discussed on FriendFeed. That's one of the best things about FriendFeed - you can follow a person and see what they are doing across all kinds of other sites, whether you participate as well in those other sites or not.

That's quite different from the way that Facebook has tried to pull items in one at a time through Facebook Connect.

Thousands of people are helping FriendFeed stay valuable even though they never use the service anymore - they synced up their other accounts and their activity there is still being pulled in automatically so their friends can view it on FriendFeed.

5. Real Time Updates

Facebook is definitely interested in real time updates, and they offer a version of real time streaming already. FriendFeed feels a lot more real time though. On FriendFeed you don't get notification that there are new messages - you get served up the messages, comments, likes and other information as they happen using a technology called Long Polling. It can be overwhelming for the uninitiated - but so was the Facebook News Feed when it was launched.

We wouldn't be surprised if some of the real time features of FriendFeed found their way into Facebook. FriendFeed's Buchheit told us earlier this year that he believes real time conversation is the next big step on the web.

How realistic is cross pollination?

We talked to Buchheit on the phone this afternoon in what was a nice but relatively superficial PR phone call. He cautioned that he "wouldn't read too much into future Facebook development" because the two companies "have different histories." But he also said that he was interested in joining Facebook's team because the companies have "the same long term view." When asked for specifics on what exactly that means, Facebook's VP of Engineering Mike Schroepfer said he had to "decline to go into specifics." But said there was "a long standing mutual admiration, both products have evolved with each other."

We fully expect that Facebook gave up a respectable chunk of stock and cash to get the FriendFeed guys into their offices and not just to keep the chairs warm. FriendFeed will likely change Facebook in important ways and for now looking at how FriendFeed works is the best set of clues we have available.