Yes, Evolution and Creationism do seem to be the most controversial subjects around. And I think this was the case even before the rise of Internet discussion boards, where it is now even more on display.
I think there are a combination of characteristics which make this discussion particularly compelling...
First of all, it's emotional. The implications of evolution are a threat to one of the simplest arguments for a deity: That there is no better explanation.
Secondly it's a discussion in which the core disagreements and means of discourse are philosophical: Naturalism versus Supernaturalism. Yet these elements are rarely addressed at the head of the argument. Instead it's the implication of each philosophy which are compared. Because of this, the viewpoints are never really able to connect which results in an endless series of near-misses in the discussion.
This is also an area of discussion which is counter intuitive until you actually understand the evolutionary process. Once you understand it the conclusions become obvious and inescapable, but until you understand it, especially if you are resisting understanding because it's emotionally disturbing, then it seems impossible.