I would like to relate my experience with him:
Past month, he put a Night Slashers PCB on auction, apparently japanese version according to the pics (note the first main item pic is wrong as it's a Boogie Wings board, the correct pic is the fourth one):
http://www.ebay.co.uk/itm/Arcade-Pcb-bo ... 7675.l2557
I won it for 471 USD.
I noticed he was not of the communicative kind, but he marked the item as "shipped" and provided me with a "cp165076139kr" tracking number almost a week after payment.
However, a week later, that number still gave a "item is not found/number not registered" notification on the Korea Post website.
So I asked the seller to check if there was not an error in the tracking info. In response, he wrote: "Like all countries. General aviation is slow updates".
But the KP website kept returning a "item is not found/number not registered" notification" the following week. At that point, I contacted the seller again to ask for a scan or just a picture of the shipping receipt with that tracking number he gave. No response. I asked again and explained I was worried, but still no reply from him.
Faced with his muteness and no registered shipment existing with that tracking number for weeks, I started to speak of Paypal claim.
From that point he wrote me:
I wait next Monday.
I go to the post office to request a return.
The full refund to you.
(I didn't know you could "request a return" from your Post Office like that, oh well...)
But no news on that Monday, so I insisted a bit to just see a picture of the shipping receipt... Seller replied:
Please stop it..
My situation was all explained.
We've lost a lot.
Your money will be refunded next week.
Do not send such a message to me anymore.
Smells shit...
As expected, he never refunded anything by himself, so I filed the Paypal claim. I explained the situation, asked again for the shipping receipt, but still no reply and he had my 500 USD in his pocket.
He had my money, I had nothing, not even a registered package number nor scan of shipping receipt, but still he dared write in Paypal:
You gave us a huge loss
It is obvious he lied and gave a fake tracking number, the shipping receipt does not exist. My guess is either he kept the board because the final price didn't satisfy him, or somebody made him an offer and convinced him to sell the board

Again, and again, I requested within the Paypal dialogue, an immediate refund. No response.
I was mad and left him a negative on eBay, where he messaged me:
You must first remove the feedback if you want refund
Fuck that shit. Paypal took care of the case and refunded me.
f*** robber who never shipped the game and kept my 500 USD for over one month until Paypal takes action... My advice is be very cautious with that Isaotaikun seller on eBay, especially if you buy some pricey rare stuff.