At least turning on sigs here has a minimal impact on how things look with the no-image rule (something I heartily approve of).
Tellingly, one of the spams that was deleted a few days ago had its wall of text with links as usual, but the sig link was to the SEO company doing the spamming. The main reason it's important to report/delete these things quickly is because what they care about is the site getting indexed by the regular Google spider run so that their URLs get higher placement in search rankings. And once a forum gets tagged as a "soft target" that doesn't delete the links, the spambots REALLY come out of the woodwork.
Equally annoying and less obvious are scout posts with no ads or links, but are simply a test to see if there's any moderation. I haven't seen many here, but another message board I frequent gets a lot of them. Usually a fairly innocuous greeting or question that almost seems on topic.
Edit: And to be marginally on topic considering the movie under discussion, I think one of the underestimated reasons that Facebook has surpassed MySpace is how well they've managed "friending" spam. I can think of only a handful of cases I've gotten on FB while it seemed like every time I signed onto MySpace, I'd get nearly instant friend requests from 3-4 girls with the same pool of profile pictures.