According to Alexa, MySpace is still at the #18 position among the most trafficked sites on the internet:

http://www.alexa.com/topsites

I'm not sure which I trust more: the Nielson report, or Alexa. Unless Nielson actually installed tracking code on each of those websites or got traffic information from the respective companies, I don't see how they generated their rankings. The same goes for Alexa. I doubt that either ranking is particularly accurate.