I found this very interesting article on Mashable showing that FarmVille, a popular casual game on Facebook, has more users than micro-blogging tool Twitter. Apparently FarmVille now has 69M active users. This means that 69M people all over the world log-in FarmVille at least once in 30 days. That’s almost 3/4 the population of the Philippines, LOL! Twitter, on the other hand, has an estimated user base of 20M. Shocking right? You’d think Twitter would have more users since it’s getting so much media mileage on traditional channels (compared to FarmVille anyway).
Quality of users versus Quantity
This doesn’t mean that FarmVille has Twitter beat. In case of sheer volume, yes Farmville has the edge. However in terms of use and actual users, I think Twitter still has the upper-hand. Farmville’s impact on the world is not that big since it’s really just a platform for entertainment. Something to do to kill time. It really won’t change society in any way except maybe raise awareness on how to farm (lol).
Twitter is being used as a tracking tool and news channel by a lot of industry leaders and influencers. One Tweet can change the course of your product. FarmVille can’t do that for you (unless they offer advergaming options in the future).
Anyway, if you have Twitter, follow me. 
Well, this simply means that Facebook has that many members/users. :p
How’s that for showing what social networking site has the most users?