Is it even possible for a reviewer to be unbiased?

What prompted this train of thought is a conversation that John and I had about a magazine that "reviewed" speakers made by a company that the editor owned part of. It was an obvious conflict of interest, and when exposed, gave a distinct impression of foul play.

But after thinking about it, they all support themselves with advertising revenues, so they all have a conflict of interest. They all have a stake in the companies they review. The only exception I can think of is Consumer Reports.

So I ask again,

Is there such a thing as an honest review?