As expected for reviews. Per statistics, reviews are always biased when the reviews are voluntary. If you get to choose whether or not you review a product, you most likely won't unless you are displeased with said product. So the displeased reviewers are more likely to post about their problems, then the happy product owners. (: That isn't always the case, because some happy product owners are here to help share experiences with the crowd, but that is usually the case with voluntary reviews.
Hm that's interesting, I never thought about it that way. Whenever I read reviews, I always look at the critical/negative parts because those are the parts that worry me the most and offer the most useful information from my experience. Amazon reviews for example (yeah yeah it's Amazon...), there are an abundance of positive reviews that all say the same thing and a few negative reviews that really talk about things the other reviews don't cover.
Aye, something I learned in statistics, pretty useful information as I am a potential business owner. =P
I personally don't leave feedback on amazon reviews, unless I have a problem with something; so when I learned that fact a couple years ago it wasn't really surprising to me, though.