"ePinions" comes to mind.

There are a few general problems.

First: for joe random website, the content tends to get swamped, and\r\nnobody really owns it. It's hard to tell good posts from others. Some\r\ncompanies have taken to posting their own "astroturf" responses in an\r\neffort to muddy the issue.

Second: for a given website, the information can be taken down\r\neither on a single or group basis. Spreading something among many sites\r\ntends away from this.

Third: I've found that the pairing of referencing links (two similar\r\nlinks on different sites), plus email sigs pointing at one or the other,\r\ntends to produce a relatively high Google score. I've been\r\n"Googlebombing" sites in this way for a few years. It's worked quite\r\nwell in general.

Fourth: Nothing says I can't repost this elsewhere. It's also on my\r\nown website.