Apart from pron clogging up bandwidth, alt.binaries became a good vector to distribute viruses, child pron, and a bunch of other things that ISPs, and their dial-up customers, were becoming increasingly concerned about. Its openness in an increasingly more dangerous, scammy, and criminal world was always going to be its own undoing. There must have been a stage where Pamela Anderson took up most of the world's storage and bandwidth just from synchronising usenet feeds.