You're going to hear journalists use it far too much. Want to know where it came from? Language sleuth William Safire investigated for the NYT last year and concluded that the phrase was probably first used in a 1926 real estate classified ad in the Chicago Tribune: "Attention salesmen, sales managers: location, location, location, close to Rogers Park." Don't you feel more savvy now?

We're under embargo on almost all of them, but we can tell you there are at least 25 companies making location-related announcements at SXSW this week. Probably more. The Dunbar number of startups in a particular market, if you will, is something like 5. More than that and most people stop taking new entrants seriously. It's one thing to offer different technologies along the value chain of location, but sharing your location and aggregating messages by things like hashtag are two very crowded niches right now. One of my favorites is SitBy.Us, an app that lets you see where your Twitter friends are sitting in a conference session. That's pretty cool.

You've got to wonder if and when Location will Jump the Shark and what consumer exhaustion for it might mean for the long-term prospects of the market. Everyone wants to be "the Twitter of SXSW 2010" but the fact is that SXSW represented a statistically insignificant increase in Twitter usage, historically speaking.

There are loads of ways to post your location but it's very hard to get a feel for who exactly is where. SimpleGeo launched a site called Vicarious.ly today that aggregates check-ins across scads of services, all around Austin. It doesn't work very well, though. SimpleGeo's Matt Galligan told us today that the site is really just a proof of concept and that our perception that these startups aren't playing very nice together is very true. "And it's a real shame," he told us. It's hard for a 3rd party service to clearly identify whether these competing services are really talking about the same location, for example. No one tells their users what users on competing services are up to in the same location. Gowalla's Josh Williams says he doesn't know what the problem is and that Gowalla is very open about user data by open standards.

Update: Galligan pinged us after publication to clarify: "I mostly meant the problem with venue data was because of how awful the *business listings* market is. There's certainly issues with non-connecting venue data but it's a *very* hard problem to solve, so I don't blame them right now. It can, however, be solved in the future."

If you're thinking of going to a place, or you're there and wonder who else is, what you need is a place where you can see who has checked in there across all services. For the place to be at the center of your experience, not the service. Michael Arrington says the new AOL Lifestream lets you track particular locations, but that service only supports Foursquare among location services. What we need is something like that across any and every check-in service. That's the kind of thing that data standards can enable.

Google's Chris Messina told us that the Activity Streams standard has a namespace for "place" and would probably add support for GeoRSS soon, but that so far Google Buzz is the only location service that seems to be supporting it.

Gowalla's API is read-only, meaning that 3rd party apps can't publish check-ins to the service like they can to Foursquare. Gowalla says they are working on it, but they are the underdog already and this isn't helping. AOL's cool new Lifestream product, for example, only supports Foursquare, not Gowalla. That's a real shame. You know what's nice about Gowalla, though? You can see who has checked into a place and when, even if they aren't friends of yours. That's not something that's easy to do with Foursquare at all. It's also much prettier than Foursquare and uses peoples' full names, instead of grade-school-style first names and last initials. Gowalla's API just isn't seeing the adoption that Foursquares is, though. Have you seen Avoidr.org for example? That's pretty funny stuff and it's built on top of Foursquare.

If location based services ever become popular with the mainstream, every urban area might end up looking like the Foursquare map of downtown Austin this weekend. That means services are going to have to come up with creative and interesting new ways to make that data usable day-to-day and not overwhelming.

Likewise, when you think about the future, imagine Facebook being a player in this market, because they are going to be soon. It's possible that Facebook and Twitter could be where all these other services meet-up. Brightkite has different features than BlockChalk but we can see what our friends are doing across any of these apps on Facebook, perhaps. And Facebook is where your mom checks-in, if she's not an early adopter.

Finally, will location tracking be persistent? Loopt right now uses mobile carrier tie-ins to track your location constantly and expose it to a circle of trusted friends. Is that something that all services will enable in the future? Gowalla CEO Josh Williams told us "no way" does he think that will be the dominant model, but Adam Duvander, author of the forthcoming book Mapscripting 101, says he agrees with Loopt: that the value in persistent location tracking will be so compelling that everyone will end up going for it in the end, once proper privacy settings are figured out.

What do you think, do you think persistent location tracking is the future of location based services?

These are some of the things I'm thinking about location this week.