Facebook's staggering usage growth continues unabated, as the company surpassed the 100 million U.S. unique visitor milestone in November, the first time the social networking site exceeds that monthly mark, according to comScore.
Along the way, Facebook displaced Aol as the fourth most popular Web property in the U.S. Google, Yahoo and Microsoft occupy the first three spots, in that order.
"In November 2004, [Facebook] had a U.S. audience of about 2 million visitors and today it stands approximately 50 times that number. Perhaps even more impressive is that clear acceleration in growth we've seen over the past year along, in which Facebook has more than doubled its U.S. audience," wrote comScore official Andrew Lipsman in an official blog.
Facebook has also increased its share of U.S. users' time spent online, from 2.5 percent in November 2008 to 5.5 percent last month, according to comScore.
It will be interesting to see what impact, if any, Facebook's new privacy controls and default settings, rolled out last week, have on the site's usage.
Some critics have pointed out that, along with simplifying its privacy settings, Facebook has made some information public whose display people previously could limit. Facebook argues that its changes will increase usage by both making it easier for people to control access to their postings and to find people they know.
For example, Facebook is making some basic profile information publicly available, including name, profile picture, gender, current city, networks and promotional "Pages" a user is a fan of. The idea behind this is to help people distinguish among members who have the same name.
Initially, Facebook also made public by default members' friend lists, but added the option to hide these lists after people complained. This basic public information also became available to third-party applications built for Facebook.
The company also has made it possible for people to give an individual privacy setting to every piece of content they post on the site, a move that has received widespread support.