Techcrunch is reporting that Facebook now has more global users than myspace - http://www.techcrunch.com/2008/06/12/facebook-no-longer-the-second-largest-social-network/
Both are now sitting at 115m unique users worldwide.
The majority of Facebook's huge growth is coming from outside of the US - where myspace and Facebook are growing at a similar rate.
From the article: "Facebook added 75 million monthly uniques over the last twelve month, but just 13 million of those visitors are located in the U.S. MySpace added 5 million U.S. uniques during that period - at this rate it will take 4+ years for Facebook to catch up to MySpace in the U.S. market."
Myspace is fighting back with a redesign that is set to drop sometime soon, seeing the site remove a lot of the clutter and become a cleaner platform. They have also actively courted the developer community to bring some innovation to the site through third party apps ... a strategy well executed by Facebook.