I agree with seti, a lot of bad reviews criticise product functionality, when it wasn't even advertised in the first place that they even have that functionality! Or they write a bad review simply because they do not know how to use the product!
Example: A friend of mine wanted a magnetic window cleaner, ie, you put one half on the opposite side of the window, and the magnet on the inside allows you to clean the opposite side. A lot of reviews said it didn't work... turns out, the advert said "this product will not work on double glazed windows" but people had ignored it and tried to use it with them.