Facebook, with more than 31 million active users, averages over 100,000 registrations per day - 3 percent growth per week - since January 2007, according to figures the social-networking site released this month, reports MarketingCharts (via Poynter Online's E-Media Tidbits).

And over half of those users are not in college.

The number of active users has doubled since the site opened registration in Sept. 2006, according to the figures.

Some other data tidbits released by Facebook:

• More than half of Facebook users are not currently enrolled in a university or college.
• The fastest-growing demographic is the 25+ age group.
• Facebook is the sixth-most trafficked site in the United States*.
• Users spend an average of 20 minutes on the site daily*.
• The site is the No. 1 photo-sharing application on the web*.
• Photo application draws more than twice as much traffic as the next three sites combined*.
• Canada, with more than 3 million active users, has the most users outside of the US.
• The UK has the third-largest user-base, with more than 2 million active users.
• Over 1,800 applications have been built on the Facebook Platform.
• More than 75 percent of Facebook users have used at least one Facebook application.

The full set of data released is available via Facebook (pdf).

*Source: comScore Media Metrix