Ask HN: Where do you go for disucssion about a particular domain?

I often get to a website and I'm looking for background info on whether it's trustworthy, who's behind it, etc. I'd often just like to post a question to other users of the site, or a warning. It seems like there should be a forum (or even a Better Business Bureau type thing) for the discussion of individual websites, and maybe a browser extension to enable interaction with the "forum page" when you go to the website. I guess this is related to web annotation and curation which I guess are areas of stalled progress. Anyway, does something like this exist?