I think the comments are a horrible idea and could really ruin the Google brand. You can use Youtube as a case study. They have an active community and a flag

I think the comments are a horrible idea and could really ruin the Google brand. You can use Youtube as a case study. They have an active community and a flagging system but there are still several- ahem - questionable comments on that site. Attaching use generated content to search results just seems like a bad idea all around. The ability to switch the feature on and off is good but maybe the comments should be left out altogether unless they have a great moderation system- which they do not.