Forums did a a large enough chunk of what usenet did, but with nicer interfaces and easier moderation. The value-add of usenet wasn't high enough, once message passing wasn't actually necessary for data transmission.

Well, usenet isn't really dead per se, though it's admittedly not what it once was. Some of us still use it, and some newsgroups still have nice communities to them and are still good sources of information. True, many groups are overrun with spam, and in my experience it seems to attract a disproportionate number of lunatics, but it's still got its good parts, and I think it's a shame that so many ISPs are dropping it as of late.

It's not dead. I asked a question about a freezer cartridge on a Commodore 64 newsgroup, and another question about a Star Trek episode, in the past 6 months.

Both replies were exactly what I wanted, and both questions were successfully answered with no spam.

Spam, & people too stupid and/or lazy to download dedicated clients.

Signal to noise ratio mostly.