Actually, I've noticed several downvoted posts in my short time here. Caveat: I think this is more a result of trollish posting in many of the cases, but of course that is another problem on its own.

See:

http://news.ycombinator.com/item?id=507278

http://news.ycombinator.com/item?id=507604 (the downvoting on this does seem questionable, although it is an extreme position)

http://news.ycombinator.com/item?id=507301

http://news.ycombinator.com/item?id=505452