marbles88 - 4:45 am on Apr 8, 2007 (gmt 0)

To isolate one factor, I don't think that Wikipedia's rapid increase is that big of a mystery.

A few weeks ago they put rel='nofollow' on all of their outbound links. Then, a couple weeks later, we started, for the first time, to see them rank up. Many Wiki pages went to the top of the rankings after that, more because of site rank than individual page rank. If you look at their inbound links on a given page versus others in the results, they're not always that great. It sounds to me like Wiki was bleeding away pagerank at both the site level and also the page level prior to their change in policy.

This was, in effect, a highly controlled experiment in the weighting factor of outbound links.