One problem that all of us with user generated comments have is spam. Huge quantities of spam, I spend hrs policing comments (yawn). Wouldn't it be a great webmaster service if Google, in say webmasters tools, allowed domain webmasters the ability to turn off searches like "add comment" (and the other usual UGC add expressions).
Because this is how spammers find the sites to try their wordpress exploits or comment spam attempts, they do a simple "add comment" search which gives their scripts a nice long list of URLs to try. Google could give something nice and useful to webmasters if they did this, and make the web better!