What's the advantage of this versus the web of trust on bitcoin-otc? It seems like it'd be very easy to inflate your own ranking on your site.
As others already said, you should be suspicious of ratings - they are a guideline only. But, you cannot rate yourself, and I do have ways to detect people self-rating themselves. If you are suspicious of anyone's rating in this way, I will check it out in more detail.
I do GREATLY encourage people to leave ratings with specific websites and URLs, if any. Specifically, I am thinking of "for sale" threads on the forums. That will help give some verification to the transaction behind each piece of feedback, and hopefully make some of the legitimate feedback pop out more.
I am also thinking about revealing the names of the people giving ratings, to help people "self-verify" that another person's feedback is legitimate. I would appreciate feedback (lol) of whether I should make use of that feature or not.