Reddit seems to have been going downhill for some time, probably because, as it became more mainstream, it attracted more stupid people. It has previously been demonstrated, most notably with UseNet, that stupid people tend to destroy communities. Remember, kids, stupid people kill.
The same thing, of course, happened to Digg; the average IQ of a Digg user seems to be about 80, and falling.
Anyway, a few days ago, it announced its intention to start using ads. Of course, this was inevitable; there was no way it could fund itself forever. However, I suspect it will drive people away, a bit.
Possibly Y Combinator's fake Reddit will benefit.