We had an inkling this CityVille thing our mom keeps sending us requests in would be a big deal, but we underestimated just how big. After launching and quickly overtaking FarmVille's active monthly user count, Zynga's latest casual hit has now approached "sensation" levels of interest: it's enjoying over 100 million active users right now.

Casual Gaming reports there are now a total of 100,064,578 monthly active users. FarmVille's active monthly user count hovers around 57 million. Now, in case you don't quite get how big a deal this is, know that CityVille only launched on December 2, 2010 -- FarmVille's been on Facebook since June of 2009. So, in under seven weeks, Zynga's managed to usurp the most popular game on Facebook and almost double its user count.

Actually, now that we think about it, can you usurp yourself? Eh, we're sure Zynga's far too busy counting cash money to ponder such matters.