A million new users will bring a few sociopaths. Until recently we had complete anarchy with selfregulation. Now some human will have to look at everything and decide what to post. But it's not necessarily censorship. In this respect communication in cyberspace is closer to ordinary publishing than to a new realm of freedom.
Commercial advertising presents a different threat to the freedom of the Internet.
It appeared on rec.arts.erotica and on the antiBarney alt.tv-dinosaurs.barney.die.die.die. The network was bombarded with thousands of protest messages from outraged users. There's no good way to stop him. Usenet groups could be swamped with advertisements that would drown out noncommercial speech, and the rich discussion of common interests that now takes place would wither away. In real life, freedom of speech is also limited by libel laws.