Go here
http://resolutioncenter.ebay.ca/
and open an Unpaid Item Dispute.
You have to allow four days before you can open it, and another four days before you can close it. Personally, I contact the customer on Day Three and if there is no satisfactory response, go for the Dispute as soon as possible.
For the record, I find that about half the customers pay up on contact, apologize and leave positive feedback. The rest disappear forever.
The deadbeat gets a Strike on his buyer's account. Many sellers have an automatic Block against bidders with UID strikes. Take a look at your Seller Preference to Block various kinds of problem buyers. If a member gets "too many" Strikes, he loses his eBay membership.
He will not be able to leave feedback. Neither will you, but you could only leave positive FB anyway so no loss.
