Gave a little thought to this earlier.
I saw a couple ideas that were interesting such as requiring drivers licenses. 2 problems with that idea (and several like it).
1 - Getting fakes made up is fairly easy.
2. It puts the onus on AZ to verify and police this. Thus, it makes them MORE responsible.
Payal, although imperfect is pretty darn good at protecting it's users. I could probably retire on 5% of what they spent this year in fraud protection.
Reguire all sellers to be Paypal Verified at a minimum. There is some other level you reach after you have made several successful deals which makes you sales protected. Contacting Paypal would be a good start. I am sure they have good ideas.
AZ could also completely take over the sales, sign up with Paypal and have everything protected. Although this gives them more control, it also give them more responsibility which I don't think they want.
The other good idea I saw was using an Escrow service. AZ could require anyone who is not a long standing and verified member of AZ to use this service. Just like you have "Club Member" tags under their names you could have "Verified Reseller" or something like that.
Another is requiring anyone who sells on AZ to do it only through their own website. It costs very little to setup a site and under $100 to have it hosted for a year. And yes that is true. I just bought my with a rather nice website for X-mas all setup and ready to go, even has tons of content already there. It cost me $25 for the site and $81 a year to host. Domain Name renewal is about $10 a year. And from what I see, it will be pretty easy for her to change and update.
Sounds like a Disclaimer is useless so maybe everyone who sells has to sign a waiver absolving AZ from any liability or damages. That sounds like a pain though.
I have several other ideas as well but I would think the AZ staff would want to remove themselves as much as possible and not get into the cue sale business. Unfortunately, for every decent idea I had (including those above) I also saw holes.