Just one month ago at Web 2.0 Summit, Mark Pincus, the CEO of Zynga, told the audience that the company had surpassed 150 monthly active users. One month later, the company’s user base has grown by a third, rocketing it past 200 million users. Monthly active users are a relatively broad metric when analyzing a company though, as daily active users are a more effective metric for measuring a company’s ability to monetize.

During the same period when Zynga’s monthly active users grew by 50 percent, daily active users grew approximately 27 percent from 47.8 million to approximately 61 million. All other things being constant, Zynga’s revenue should grow proportionally to the growth in daily active users. When it comes to total daily active users, no company comes close to Zynga. The second largest company is Playfish, who recently sold to Electronic Arts for up to $400 million on estimated annual revenues of $30 million to $40 million.

That means Zynga should easily be making more than $250 million annually at this point, although the company recently took a hit as Facebook became more aggressive on some of the questionable IQ Quiz advertisements. The company also had Fishville shut down for a few days after Facebook found advertisements which violate their advertising terms. That application has recovered though and is growing at upwards of 10 percent a day, currently reaching over 12.3 million monthly active users.

Under two months ago we wrote about Zynga surpassing 100 million monthly active users and the growth isn’t slowing. At this rate we could be talking about the company surpassing 500 million monthly active users in only a few months. With the company’s rapid ascent, a projected 2010 IPO doesn’t seem so ridiculous.