RockYou on Businessweek
Anastasia (the author of the article), not sure that I agree that widgets are "parasitic in nature". Parasites don't give back to their hosts. Widgets increase user engagement and functionality for a social networking site. The more breadth of widgets, the more a user can do on MySpace for example. That aside, a nice primer article for those who haven't a clue what the heck a 'widget' is.