[nights] Like everything, it's been mostly full of crap since it started, but it's only been in the last few years that the crap has expressed a desire to leap down everyone's throat.
The big cautionary tale of the net is Usenet, which although some people manage to keep active newsgroups going (using I don't know what antispam measures), is now almost entirely spam. I've been working recently on a little predator/prey population interactives, and I wonder if the cycles of spam-genuine content follow a similar statistical pattern. i.e. the population of predators increases, diminishing the population of prey, which in turn leads to extinction for the predators...
[Projoy] I think part of the problem with Usenet is that most people aren't even aware it exists any more, and those who are aware of it, by and large, consider it too full of spam to be useful. For this reason, I don't think you'd find a cyclical pattern, but rather a gradual tail-off with time.