To be frank my classified experiences with members has been worse than with non-members, in regards to payments, stated item condition, etc.
I've been taken for a ride more by members than not, and like the fact that the classifieds are open to more people than just our member base. If I were to base an individual's reliability on whether or not they are a member, then in my experience I'd rather buy from non-members.
There are many folks who "lurk" on this website, read the forums, use the classifieds, etc and end up becoming members eventually.
I just bought some items from a gentleman in Missouri who isn't a member, but has more knowledge about Dodge diesel pickups than many on this site, and IMHO I could care less if they're a TDR member or not, as long as the deal goes down correctly.
Just my 2 cents, but the classifieds should stay as they are.