Foursquare Hits 5 M. Users. Growth Strong But Flat

foursquare gap ad Foursquare Hits 5 M. Users. Growth Strong But FlatFoursquare just hit five million users, a great milestone that shows the company’s growth is not slowing down.

Unfortunately, it’s not speeding up either. It took a year for the company to reach one million users; three months to hit 2 million and a month and a half to hit 3 million.

Since then, however, it has added 1 million every 1.5 months, so user growth seems to have leveled off.

When Facebook debuted its Places platform, many in the tech press, The Observer included, speculated about what it might mean for Foursquare.

But the last quarter of 2010 has been great for Foursquare. It locked down major partnerships with big brands like Gap and Radioshack, added an office in Cali and brought on new hires in NYC.

Founder Dennis Crowley just tweeted that his company is working on a hot new Foursquare app. Now they just have to worry about alienating those core users…

UPDATE: Foursquare’s Erin Gleason writes to say, “Although we’re over 5 million in terms of user IDs, we haven’t quite hit 5 million users yet. We should hit 5 million sometime next week.” Devils in the details.

bpopper [at] observer.com | @benpopper