Spam is hard. No real platform has solved it completely, and none ever will. Spammers evolve, platforms catch up, spammers evolve again, and so on until the last post is posted and the last user signs out. Individual spam tactics, however, do tend to have short lives, and while PIB won’t be with us forever, it’s notable that it has been with us for so long — a consequence, perhaps, of the near-total elimination of the teams that used to deal with such things at Twitter. Long enough to become a platformwide joke. Long enough to become genuinely sort of annoying even to the users who think it’s funny. And long enough to get some idea of who is posting all that P in all those B’s, and why.