Equipment reviews, are they credible?

Maybe I'm just thinking outloud but; do all these new equipment reviews have any value? If someone you do not know reviews a piece of gear for which he has spent a significant amount of money can his opinion be trusted. I'm not suggesting the person is lying but I think people have to justify (at least in their own minds) the money they spent.
Then there is the issue not knowing the person doing the review. We don't know their personal preferences or their perspectives. As I read these forums I see there are some names that continue to pop up that give good advice, there are some whose advice is not as good, and some people who are idiots.
How do you know which of the above categories the reviewer of the piece of equipment comes from?
With money having been invested and credibility in question, who can we trust?