Great article. This is a response to comment #1: The idea of a larger auction site somehow offering more security and protection is pure fallacy and it's just untrue. The smaller auction sites that accept credit cards, have to go through rigorous security checks to ensure their customer's security. The security check list is overseen by the merchant account provider so if you do not comply in any way, you will not be able to accept credit cards. These security check lists are needed because they protect the consumer.
An overlooked security risk that people need to be aware of is the practice of storing credit card information. I believe that some of the smaller auction sites that do not store credit card information have the security advantage. Any time a company stores your credit card info, you run a risk so please be aware of this.
As far as people backing out on their bids, you will no doubt have this (buyer's remorse) but I'm sure the auction site will be willing to re-list your item for free because its just good business to do so.
I would rather deal with a mom and pop type store because a lot of them are willing to go out of their way for the customer.
A site's pricing page is very important; it should be easily understood and clearly outlined as should the terms and conditions. I agree with the other comments as far as doing your research on these sites, you have to because you can never be too careful.
With any ad site, it's "buyer beware," so you have to be careful and use common sense, no matter how good a deal you got. If you find something but have reservations, get a phone number and call the seller. If they are not willing to give out that information or at least talk to you, then something may not be right and it's not worth your time.