The New York Times today gave a heads up on a Pew internet report from Dec that says "Girls continue to dominate most elements of content creation. " http://www.pewinternet.org/PPF/r/230/report_display.asp
The Times offers possible explainations. http://www.nytimes.com/2008/02/21/fashion/21webgirls.html
They also offer sites like this as example: http://sodevious.net/
Just looking at Second Life and this all comes as no surprise.