If you're interested in Facebook's announcement this evening, you can watch the proceedings live here on the Forrester blog at 5 pm PDT.

The social media world is abuzz.  Take one hot trend (geolocation) and add one blazing hot social network with a history of privacy missteps (Facebook), and you have the making for an interesting news story. 

That's not the only reason curiosity is high about tonight's event--there's also a lot of money involved.  While consumer adoption of geolocation check-in via services like foursquare and Gowalla is still nascent, there is little doubt that consumers will increasingly share their location via social networks.  They share their profiles (who), their activities (what) and their hopes and wishes (why), so why not the "where"?  And this data becomes yet another piece of the puzzle for advertisers wishing to build promotions, loyalty programs and more personalized and targeted advertising.

Then, of course, there's the foursquare vs. Facebook angle, which I expect will disappoint those looking for a battle royale between the heavyweight champ (Facebook with 500 million users) and the young upstart (foursquare with 2.5 million users).  Facebook seems less likely to launch a "foursquare killer" and more likely to create a geolocation platform upon which others might build.  Think of it this way:  Facebook doesn't create social games, but instead creates the platform on which third-party social games thrive.  Despite the Facebook vs. foursquare hype, the two are likely to end up more complementary than competitive.

But for all we know, all this buzz about Facebook's geolocation offering may be just so much hot air.  We don't actually know what Facebook is announcing, so even though a geolocation service has been long rumored, Facebook might just have a different trick up its sleeve.

Find out here tonight.  Tune in to the Forrester blog to watch the news event live: