My partner and I are working on a site featuring 3rd party services that will include user reviews of those services. Some of the service providers we would feature (our customers) have suggested that we should not allow anonymous reviews.
On one hand we agree that it would be great to be a forum supportive only of reviewers who are willing to stand behind what they say.
On the other hand, we think (1) it would be difficult to verify a reviewer's identity and (2) that review readers will tend to discount anonymous reviews on their own anyway so it will all come out in the wash. By that reasoning, there is no need for us to police reviewers, except for obviously inappropriate content or manipulative conduct.
We would love to hear how others think about this issue.
The decisions you make regarding review quality will set the tone of your site. You can do absolutely no verification, e-mail verification, Facebook verification, you could even require a scanned license if you wanted.
Which one you choose depends on your target audience. For example, a website for doctor reviews might be able to justify more verification than a website for laptop reviews. You should try to survey your target audience to see how they feel about it. But be careful, users sometimes don't know what they want or need, nor do they know what is best for your business.
In my opinion, a website centered around reviews will live or die based on the quality of its reviews. Yelp has an amazing, but often overly aggressive automated filtering system because it believes this also.