Look at the image above. There are three services listed on the San Francisco Giants' scoreboard during a baseball game. Twitter. Facebook. Foursquare. The first two are ubiquitous. Each has hundreds of millions of users and a firm place in pop culture. The third has about 2.5 million users. And much of the world has no idea what it is. But is it on its way to entering that pantheon of great services? This is a particularly interesting question given that on Wednesday, Facebook is expected to unveil its initial push into the location space. Earlier, BoomTown cited sources stating this would be the case. We've since heard from multiple source as well that location will be at least a part of Facebook's event (which we'll obviously be at). With location, Facebook has long been seen as the 800-pound gorilla in the room. And now they appear ready to check-in for the first time, as it were. So Foursquare is dead, right? Don't count on it.