To bring up a very small point in Vladimir's otherwise very handy post, I think there is very little actual abuse of logical fallacies. Most people using logically fallacious arguments are unaware that they are doing so, and I think this is the root cause of most fallacious arguments on this forum.

Some people may be using logical fallacies on purpose to further an agenda - for example in religious arguments or when a large amount of pirated money is at stake. However, most of the time I think most people involved in presenting illogical arguments here are unaware that they are not arguing logically (or rationally). Hence the importance of Vlad's summary of logical fallacies. This should be a sticky in several boards I can think of. As well as some politeness rules.