Facebook is readying to launch its Foursquare competitor in a few weeks, according to CNet. This is probably the main reason for Mark Zuckerberg's company-wide 60-day lock-down.

Caroline McCarthy picks up several hints about what the offering will look like: It will be an API for use by third-party apps. It’ll have an events check-in dimension, thanks to the Hot Potato acquisition. It’ll integrate existing “check-in services” more deeply into Facebook.

That last bit means it will repeat the “open social graph” bargain with the rest of the Web: you tell us who’s visiting your site, and we’ll tell you who their friends are. With geo-location, that becomes: you tell us where a person is and we’ll tell you where their friends are. We may even tell you what direction they’re heading in and how fast they’re going.

Two ways this will impact culture as we know it: 1) You’re bored, you want to hang out. You don’t need to call. Just show up. 2) Parents can know where their kids are at all times (except for the occasional cell-phone drop-off).

A big question, as always, is Facebook’s privacy settings. Will you be able to let just select friends know where you are? What are the defaults, and how confusing will the control settings be? Contrary to what some might think, Facebook will be as pro-privacy as possible in the beginning, in order to get early adoption and avoid bad press. Later, they’ll release updates and slowly get people accustomed to being open about where they are by eschewing privacy, the same way they’ve done with all personal information.

That will be a great boon for marketers and intelligence services.

This likely means that Foursquare will end up regretting it didn’t take that rumored $120 million buy-out offer from Facebook when they had the chance. If it weren’t for Crowley’s distaste for Google, he could have hoped that Google would buy Foursquare in a social-location catch-up bid.