Forum Moderators: Robert Charlton & goodroi
It appears that some people discovered that such pages were able to acquire several thousand links in a couple of days and were then allowed to rank instantly, what with being on a trusted subdomain.
I noticed Matt Cutts brushing the problem off in his blog a few days back, but they clearly were concerned at the 'plex and have now just banned all the user generated pages within the subdomain with a new robots.txt.