According to a “source”, Silicon Alley Insider posted recently that Facebook was working on Foursquare-esque check-in functionality. While Facebook has not officially commented, I think there’s little doubt this will actually happen. The article points out a few reasons why Foursquare should be worried.

For one thing, Facebook is something you (probably) already use, and you’d be sharing this information with people that are already your friends. Convergence of your existing Facebook account and check-ins could eliminate the need to use one or more other apps. And it follows one of the tenets of social media apps, in that you’re going to gravitate to the apps your friends are already using. As much as I used to like Pownce, hardly anyone I knew used it….and so neither did I.

The other point, and this is the one the strip makes, is that Facebook “can afford to fail”. With their engineering talent and money, why not throw some developer’s time at a “beta” check-in app? If it takes off, great. Foursquare then needs to evolve, and fast. If not, whatever. It’ll just get thrown on the pile of other stuff Facebook is surely working on that we may never see.