A few years ago I was a moderator on a forum and the admin refused to implement any spam blockers or filters, needless to say the site was so over run with spam it had to be shut down. While it was still active, I would delete a spam post and 20 more would appear. It got so bad I walked away and just let them spam take over. I checked up on it about 6 months later and the site no longer existed. Whenever I see spam, I try to report it right away, otherwise it can get out of hand and I've seen first hand what out of control spam can do.