Yes, there seems to be a lot of that happening these days.
After a hiatus of several years not selling, I've recently been having a clearout of accumulated odds and sods and I've had three people win things recently and then just not pay or respond to polite requests.
I had something the other week on a 10 day auction, starting price £10 and one character almost immediately contacted me and asked if I would accept a BIN so I replied yes, £20 and it's yours.
He responded with a sarky comment saying it was not worth that so fair enough, it was his choice and I ignored it.
Then, three days before the end of the auction he puts a bid in and then says that he will now do a BIN at £20 so can I change the listing.
Well once a bid is on an auction listing, you can't edit the listing to put a BIN on, so I asked him to retract so I could edit it to do so.
No response, nothing.
Anyway, on the day of the auction, others started piling on their bids and outbid him and sure enough it climbed to £20 which is pretty much what I reckoned was its worth, until the last few seconds when matey boy comes along and wins with a final bid of £21.
Then, nothing, silence, no response to polite messages asking about when he was going to pay.
And there seems to be absolutely nothing you can do about it, ebay seem uninterested and simply say to relist it.
You do wonder about some people who are out there.
If it was a real shop you were running, you at least could probably spot these characters when they walk in through the door.