Whether you like affiliates or not, they are a driving force behind traffic to many successful sites. As far as affiliate in forums I think its ok too. Not all affiliates though. Only the affiliates who understand contributing to forums in a positive way increases traffic to their site and boost credibility as well as benefiting the forum.

Affiliates get my vote, only the good ones at least. The rest… they suck, AND, they ruin it for other affiliates.