Has a payment-that-is-not-guaranteed really arrived? Users have been tricked sooo many ways.
Discussion
What if the software used 3 or 4 visible nodes to verify the transaction while its syncing?
Like, the wallet could start downloading blocks from the beginning to sync AND from the current time to quickly verify. If all connecting nodes agree that this is new, the risk should be minimized to almost zero.
It's a beautiful process but not perfect. I don't follow the details but know it's been worked on since the beginning.