Facebook is integrating location data so that users can write location-specific updates, the company announced today. The new feature, Facebook Places, is already being rolled out in waves to users in the United States with international support to come, and an interface so that developers can start using location data in third-party applications is coming tomorrow.

Facebook may be moving fast, but Zuckerberg and co. are being careful to ease their 500 million users in - making nice with location pioneers Gowalla and Foursquare; emphasizing user benefits, not marketing possibilities; and sharing gooey anecdotes about how Facebook Places creates a living history of the world.

This is the Facebook you love, the company said today. The one you check every day, the one that connects you with people you haven't spoken to in a while. The Facebook that makes your life better.

What is Places?

Facebook Places are locations in the real world that users can now "check into" from their mobile devices, much like Foursquare or Gowalla. Each location has a Places page, a stream of updates aggregated from what users post to their profiles, and a "People Here Now" section where users can see who they know who might be there.

Users can add locations that aren't in the database, powered by local business listings provider Localeze, claim establishments they own and report locations that aren't kosher (such as someone's apartment).

Places is available already to some users, using the most recent version of the Facebook application for iPhone or from touch.facebook.com in a mobile browser that supports HTML 5 and geolocation. There is already a read Application Programming Interface for developers, and write and search APIs are in the works, so expect a wave of location-savvy apps to start sprouting up immediately.

User control

The new Facebook Places is "opt-in," which in this case means Facebook assumes you want to be part of Places and share your location information with your friends, but not necessarily the whole Internet (we're working on a "How to disable Facebook Places" post now for those who aren't ready for the location revolution).

Users decide whether or not to check into a place. But they can also "tag" friends who (in theory) are with them. The first time this happens, Facebook will ask you if you want to allow your friends to check in on your behalf. Say yes, and the tagged check-in will post to your profile. Say no, and the tag will only show up on your friends' pages. You can change your settings to disallow tagging entirely.

Baby steps

Facebook has introduced this feature in a compelling way to mainstream users who are learning and loving the social web, and it seems destined to be a raging hit.

A lot of attractive possibilities open up when users share location data.

There are the badges and the passport stamps - the fun of "life is a game and I just leveled up" exemplified by Foursquare and Gowalla.

There are the social advantages of knowing your friends are at the same concert.

There are the productivity enhancers like to-do lists that remind you that you need to buy milk as you walk by the grocery store.

Now add the potential for better maps, better news gathering, more granular police work and more ways to organize data on the Web.

On the other side you have more efficient advertising, a trove of intelligence that could be hacked or subpoenaed, and an easy path for some of the Web's cliques of overly like-minded people to bring that insularity into the real world.

But most users will see the feature in its initial manifestations - advertise the fact that you saw Lady Gaga last night, or discover that a new food cart has opened near your house, or see who else is at the bar - and click yes, Facebook, opt me in.