Just a few months ago, social networking behemoth Facebook announced that it had reached 200 million users. Now, just over 3 months later, the site has reached 250 million users, acquiring up to 750,000 new users per day in recent weeks.

And though much of this growth (approximately 70%) has come from outside the United States, the site is now the most visited in the United States where it is the undisputed #1 social networking site.

“For us,” says Facebook creator and CEO Mark Zuckerberg, “growing to 250 million users isn’t just an impressive number; it is a mark of how many personal connections all of you have made, and how far we at Facebook have to go to extend the power of connection to the billions of people around the world.”

So, everybody’s jumping aboard the social networking bandwagon, and Facebook is the leading platform, but what about engagement? Facebook reports that users spent an average of 4 hours, 39 minutes on the social network in June 2009, that 20 million users log in at least once a day, and that 30 million update their status daily, making the company’s apparent inability to fully monetize all the more mystifying—though there are hints that the floodgates of revenue may be opening soon.

Read Mashable’s take on this impressive milestone here.

Read Facebook creator and CEO Mark Zuckerburg’s blog post here.