wheel - 4:52 pm on Apr 10, 2010 (gmt 0)
Not that I'd know, but I've never heard of such a thing. I don't see the benefit of such a penalty anyway. I doubt it's an issue with the SE's.
To put it another way, being able to discern a nofollow penalty would be bad for the nofollow tag anyway - such blatant manipulation by the SE's of the use of the tag (in direct contravention for what they've stated is the intent) would lead to all sorts of mistrust.