Popular social media sharing site Foursquare has announced that it now has 20 million users, who have checked into more than 2 billion locations.

“In 2010, foursquare fans declared April 16 4sqDay (4/4^2 – nerds after our own heart!). Two years and two billion check-ins later, you’re still why we get out of bed each day. Thanks to all 20 million of you for making us part of your lives,” a message that was posted on the company’s official blog read.

Despite other social networking services such as Facebook adding check-in services to their sites, Foursquare has continued to grow its user base. Foursquare launched in March 2009 and went on to reach the ten million user mark in June 2011. After taking over two years to get to ten million users, it took the company less than ten months to double its user tally.

In other social networking related news, Facebook recently announced that it is acquiring photo-sharing app Instagram for the cool total of $1 billion (R7.6 billion), made up of a combination of cash and Facebook shares.