Just after its recent 2012 retrospective  PR push, Twitter  earned a little seasonal gift--reaching the milestone of 200 million active monthly users. Fittingly framed as a tweet , Twitter thanked its users and noted "you are the pulse of the planet. We're grateful for your ongoing support!"
Twitter's been quietly growing its user base. In July 2012 the site had some 170 million users among its 500 million registered accounts. The active user tally  is, of course, a far more important measure of how well a site like Twitter's doing (and it's one that will play into advertiser's minds) because it weeds out people who are not actively engaging in the site's social network. This figure means Twitter's managed some 17% growth in the half year until today.
Facebook reached a milestone of a billion monthly users in September 2012, but the way it accounts for its active users remains somewhat controversial , as the figure may be overly inflated by web apps that link to Facebook.
[Image: Flickr user luc legay ]