This news about the number of active particpants on a social website were no surprise to me:

It's an emerging rule of thumb that suggests that if you get a group of 100 people online then one will create content, 10 will "interact" with it (commenting or offering improvements) and the other 89 will just view it.

I've been involved with Wikis for years now, and that's how they operate as well. Out of your entire community of users, only a handful will add new content, or prune the old stuff. It's not surprising then that most YouTube uploads come from a small cadre, or that Digg is powered by a relatively small number of linkers.

Heck, think about any community, online or offline. How many people in the community actually do the work?