Forbes may think that blogs "are the prized platform of an online lynch mob spouting liberty but spewing lies, libel and invective." (password and login = forbesdontbug)
Blogs started a few years ago as a simple way for people to keep online diaries. Suddenly they are the ultimate vehicle for brand-bashing, personal attacks, political extremism and smear campaigns.
The article is big on blaming the medium but with or without blogs there will be some companies who will try to attack or discredit their competitors. There will be people who rant about corporations because they think that all big businesses are bad. Some people probably feel stongly enough about it to dedicate a blog just to trashing a company or product. I don't really know much about them and wouldn't base a buying decision on what a blogger with an obvious bias (for or against) has to say. On the other hand, I have bought at least a couple of things this year (a Nikon D70 and an iPod) where my decision was based in part on posts I had read that expressed satisfaction on similar purchases. These posts weren't on "product-specific blogs", they were on blogs I read regularly and were, to me, no different than a recommendation from a friend, co-worker, or neighbor.
My advice to companies is this: Don't think of bloggers as the enemy, but as potential customers. People who dislike you will do so regardless of what you do. If you provide the rest of us with a good product combined with good customer support we will sing blog your praises.