tedster - 9:04 pm on Oct 15, 2010 (gmt 0)
I'd say Google has a heuristic that looks for artificially induced "link velocity". Last year there were definitely cases of websites knocking out their competitors with this route. This year, not so much. Either they've improved things - or they just started ignoring those links instead of penalizing.
Just one man's opinion, of course, but I have worked on at least six cases like this. On the plus side for Google, a Reconsderation Request with good data brought a fast turn around, usually about 4-7 days.