nobody ever talks about double-payments:
Alice wants to defraud Bob. She goes to Bob's shop and uses her custom double-spending wallet to perform a fast-respend at checkout.
Unfortunately, Bob doesn't see Alice's
"legit" txn. Instead his node sees the double-spending txn first. Worse, it turns out that the miner who is going to mine the next block sees the legit txn first.
So Alice is standing
there while Bob waits for a valid txn. Alice has a tough choice.
She can tell Bob she doesn't want the goods any more, and leave. In a few minutes the next block will get mined and
Alice will have paid for goods she didn't receive.
Alice can send another legit txn and purchase the goods. In a few minutes the next block will get mined and Alice will
have paid twice.
Any form of double spending is susceptible to double-paying.
