Poetry Slams are a questionable
thing. I've attended some of them because they came after a regular poetry reading
The reason I think they are questionable is that the best poems are not chosen, but rather the most gripping or whathaveyou. Quality of the work, thought value, and so on, are often looked at in tie-breaker fashion rather than the primary means of judgment. Spite and angst and anger towards the status-quo, of which a sufficient amount of almost assures victory.
I guess that's just my opinion.
I do know a slew of the people that went to last years national slam in Rhode Island, and they said they had fun. I reckon that's what really matters to them.
I do think poetry readings are good for writers of all sorts, tho, because it gives immediate feedback and lets them see what the audience thinks of the work. Too much, however, and you might "sell-out" (i.e, write for the audience, not onesself).