So, I usually sell one or two items at a time. This weekend I had someone order 7 items from me. Score! This person has 3700 feedback, WOO!

This person turns out to be a non-paying buyer

How can a non-payer get thousands of feedback, and keep not paying. I'm assuming that after so many transactions this is not his first time not-paying, and on such a large order no less. Come on ebay, if someone doesn't pay often enough, boot them. If someone leaves neg feedback habitually, boot them. These things are not hard to track! You should not be able to get to 4000 feedback and repeatedly not pay for purchases.