As somebody who lacks self control
I do fit some of those categories. But sometimes is it absolutely justified because companies will do the reverse.
They will actually astroturf and promote their products which do not deserve promotion and they will manage agressively their image in a not so nice way to present themselves in a better light. Eventually the users of such things find out and leave on their own accord but they still grabbed your money for a while until the person wised up. I mean just look at Amazon, I would place a good bet that a large % of the reviews on there are astroturf fake reviews.
I feel the vengeful hate comments on review boards are just a counter balance to the company astroturfing . And they are useful, if the company is proactive they will remedy the bad experiences which made the person who wrote the review comment negatively. If not they'll just astroturf some more.
Saying this is just another excuse and another weapon to use against people who have some REAL concerns and beef with companies. I was nearly killed by the negligence of a company recently. Yet they spread around that it was me being a hot headed kid who was useless.
Unfortunately for them nobody believed them because a huge number of 'hot headed kids' were going to other places to skydive and their attempts to blacken my reputation on them backfired as it convinced even more people to go else where. Who were again labled hot headed kids.