why reviewers think they know more than the gadget makers....

I'm not being specific to any site but i'll be honest in pointing out that many tech sites downplay a gadget/OS just because he think its not right for people. Ive been following tech sites from many years and i get annoyed by people saying this gadget will fail because of bla bla bla...10 reasons why this will fail...only to know the reviewer failed not the gadget.This raises many questions

a. can a Reviewer speak for Audience (Average Consumer) and holds the final judgement?

b. on what basis a Reviewer fails a gadget or OS? lets say people who have written articles on why Windows 8 suck and will fail. or reviewers who laughed at Galaxy Note.

c. and how do the tech sites decide who will review the Gadget? (if you are going to ask MG Sielger to review a windows 8 tablet . well everyone knows conclusion is RAPE ,or any non apple stuff will be raped by him)

side note: I recently had argument with a friend who keeps posting these link why this stuff will fail. I asked him once whatever u talk about will fail happens to be successful like he used to say Android will fail a lot. he replied because"Average Consumer" is misinformed, they can be manipulated and make wrong choices.