FranticFish - 2:18 pm on May 8, 2011 (gmt 0)

I'd imagine (no proof) that Google are more interested in networks of sites set up for link schemes, whether for link brokers or by SEO companies for their clients.

If I find a network I always take a few minutes to report them. If Google act (and they do take down networks) this could not just clean up your particular SERPs, but quite a few others.