So a bunch of science fiction and fantasy writers wrote a horrible novel to send to a vanity publisher as a prank. And the vanity publisher bought it (literally). As soon as the VP caught on, of course, they cancelled the contract, but the book has nevertheless found an online publisher (albeit this time advertised as exactly what it is). An excerpt can be found here: http://nielsenhayden.com/makinglight/archives/006032.html#006032
I tell you, reading that, I feel better about my own work. All writers doubt themselves, but it's good to know that I'm not unintentionally as bad as people who are being intentionally awful.