Of course every non-moderated service has spam, that was kinda the point of my post... Maybe the part you missed was that they introduced a new way of spamming via forking pages... I don't think I ever made any allusions to something not happening because of it. Thanks for the pep talk though, I'll keep it in mind as I do my nightly task of helping clean up spam on the sites where I moderate.
Spamming via forking seems, to me, to be very similar to trackback spam on blogs. But, yes, it will probably require a bit of novelty in terms of how one fights it.
