As a buyer and a seller, I know both sides of how people feel. On one hand, you can't really list an item and say 'people with a low score cannot bid.' Because there are A LOT of new buyers or people who don't buy often.
On the other hand, as a buyer we need to protect ourselves- because there are SOOOOOO many people who are only on there to scam people! All of my listings are VERY CLEAR. If you do not pay in X amount of days, you will be reported as a non-payer.
Also, I cannot stress HOW IMPORTANT it is to get a tracking number for EVERY item you sell!!! It doesn't matter what the cost of the item is. People in the past tried to tell me that they didn't receive an item from me. There was one time the item was worth $5. They said they didn't get it. I lost the tracking number temporarily and they left a HORRIBLE review on my account. I found the tracking number and notified ebay. ONLY AFTER ebay received and reviewed the information they DID remove the bad feedback from my account and they went after the people who were trying to scam me. I didn't hear anything- but it didn't matter. Ebay had proof that I wasn't in the wrong, so they fixed it. If I didn't have that proof, I probably wouldn't have sold anything for a long time!
The tracking number is not that expensive. I usually add an extra 50 cents to the shipping, to cover the tracking.