Opinion vs review?

In this recent thread: http://forums.dpreview.com/forums/thread/3378247, a posted link was described as a review. Several people objected to this characterization, and claimed it's really an opinion, not a review.

What's the difference? What does a review need to include in order to be considered a "legitimate" review and not an opinion?

Please note that I'm not arguing the merits (or lack thereof) of the linked "review." To me, it's not very important whether people call this a review or an opinion, the content is the same either way; but I am curious about the semantics and why some people think it's an important distinction to make.