What does it take to qualify as a reviewer?

I agree with most of what Elizabeth mentions. But- It is apparent that, in many cases, ears were NOT a prerequisite.

Trying to be serious here, I'd say a GOOD reviewer would have, first of all, broad exposure to the great variety of manufacturers and designs that exist. That's a corollary of the problem with much advice given in online forums, you usually don't know how much or what background someone posting an opinion really has. Second, they'd have enough industry insider knowledge and technical expertise that they'd not recommend that readers go and buy some poorly designed product marketed by an under capitalized company bound to go belly up in the near future. Perhaps a bit of understanding about marketing and business would help in evaluation of products. After all, some very small operations have made great gear and been in business for many years and other upstarts with big budgets and grand ambitions have failed. Of course, writing skills would be a great help. Having an analytical mind that understand the basics of logic and that has developed reasoning skills balanced with the capacity for intense emotional involvement with music helps as well. As to "not having ears," I'd just chalk that up to the fact we are all different and respond to different aspects of music reproduction. Plus, it's impossible to use a piece of equipment in all possible contexts. Can a reviewer write an objective, dispassionate, and analytical review of a product that would accurately describe all performance parameters and equipment/room interactions?

Hyperbole, exaggeration, contradiction, inconsistency, cables more expensive than 98% of all subscribers systems, and a love for this insane nerdy hobby we all are a part of on some level.
Seriously, some basic understanding of music, how it sounds live, reproduced, both musical and electronic backgrounds and the ability to wax eloquence when reviewing/writing....O and lets not forget, the ability to have fun, and more fun being evaluated by readers.

I agree with all the above particularly Photon46's criteria and would add the ability to accurately and consistently articulate and describe difference between components and sonic characteristics of components in a language that can be understood by all. The key thing is that the taste of the reviewer is not nearly as important as describing what he hears. I always felt the late JG Holt was the best of all reviewers I have read in that aspect. Of course he met all the other criteria as well, writing skills, technical understanding and certainly experience with a wide range of components over years of listening.

if you want to review for stereophile, you need to be the biggest bullshit artist that you can be, need to be able to always give a good review at the end no matter if you find flaws in it, and you need to justify the piece as being the best that you have heard in your system, even if your system has changed dramatically since you last reviewed something similar. Make sure you have a thesaurus handy to modify words that are simple to emphasize your review.