I think the real question is after you use Google Alerts and find a post or comment about your or your site, what do you do.

Some people ignore the posts because you tend to spur on more comments if you fight the bloggers or whomever made the comments.

Others, will aggressively argue and defend themselves and will spend hours and brainpower doing it.

We see a lot of posts about us and I make a judgment call after looking into the traffic of the blog/site, the amount of people posting or ganging up and then if the posted comments are lies or do they have legitimate complaints (we aren't perfect so sometimes they are legitimate). When I post, I only post once, I refute the comments, post to links to information about us that is positive and I make sure everything is very well worded and very concise. What does tend to happen at that point, if it is a busy blog or forum, is that defenders of us start to come out of the proverbial woodwork.

You will lose every time you get into an argument with a forum or blog ... every time. I defend us but I do it very carefully.

You need to make the call how you want to handle it.

Arthur