The classifieds are the most popular section of the site and I welcome members who join just to participate in it. It's up to you as a seller to vet these new people to insure you are not being set up. There are many ways to do this. These days, it's rare I have to meet someone without first being able to get their name, Facebook, phone number, etc. If you are feeling uneasy about the deal just call it off. I have flaked out on buyers and sellers because I just didn't feel comfortable with it for some reason (mostly craiglist deals).
Truth. We all start at zero and that is no reflection of anything other than time on the forum. I agree that is better to have some history on the person as far as posts and feedback score but somebody has to pop their cherry. The Marketplace is a very interesting sub-forum just because of the variety of things that come available. Come for the Marketplace, stay for the discussions.