Business Week in its Web Attack article about negative word of mouth mentions a damage control company called Reputation Defender. From their site:
"First, we SEARCH. Next, we DESTROY. Our trained and expert online reputation advocates use an array of proprietary techniques developed in-house to correct and/or completely remove the selected unwanted content from the web. This is an arduous and labor-intensive task, but we take the job seriously so you can sleep better at night. "
Very reasonably priced: $30 a frag (killing and item of online content). Some insight into their methods: by Auto Admit who say they were approached by reputation advocates, and on Consumerist.