Quoted from robin:Wow, some great ideas, thanks all!
Building on these ideas, one of the easiest things to implement would be address verification. It would be another level of verification (e.g. a blue checkmark) where we ensure someones address. What we have now, the black V icon, would remain the basic verification (stops most Nigerian scammers because they don't want to shell out $5 bucks to get verified).
So how would mail address verification work? It would involve Pinside sending a postcard (automated via one of the online sending APIs) containing a code. You log in to Pinside and enter that code. Boom! Address verified.
Then I thought, postcards are fairly easy to steal, even if that's a federal offense (I mean, so is scamming people out of thousands of dollars, right?). I could also send out a Pinside mug. It's too big for your letterbox and you need to open the door to accept it. I would enter the code on the packing slip. Or print it on the mug, lol.
I estimate this could be done for around $10 (I would need to check, but it looks to be doable, at least for US adresses).
Still not 100%, but it's pretty darn close. Right? Or am I missing something obvious?
I have no use for a mug (don't drink coffee or anything like it), but a water bottle would be great 
I've bought 3 pins in my fairly short pinball life, and one of them was via PinSide. The first was Craigslist, and it was a nervous experience for me. It was about an hour away, so I brought cash and a gun (conceal and carry permit here in TX). Anyway, when I met the guy and saw the pin, I know it was legit. I made up some excuse about having to go out to my truck, locked the gun up, and the transaction proceeded. The second with my neighbor, so no issue there. The third was about a 5 hour drive and the pin was advertised here in Pinside. I had several chats, requested a phone number and address, which he provided. After looking up his address and having a couple of phone calls with him, I felt it was legit. I brought cash and my gun again, left the cash in the truck until he answered the door and I met him, then everything went down as smoothly as could be.
While I made what I thought were good decisions, I've learned a lot from the advice given here which I will integrate into my next buying process. I'm truly amazed at the level some will go to in order to steal from others. Another thing we can all do is when this or any other fraud happens is take the time to prosecute them to the fullest extend of the law. Maybe this will help the next guy think twice before doing the same thing. If not, there's always the Pinside Fight Club (see the basement topics).