Is There a Problem With Double Spending?

There's the Peter Todd argument is that right now a lot of merchants that want to prevent double spending by monitoring the network very extensively, which requires resource costs from all the nodes they're connecting to. So as a merchant, in that case, you really want to be completely up to date on the mempool more so than other nodes. There's something Sergey from Bit refill brought up, which is calls that they issue with the free American call option. If it's easier to replace the transaction, then it could have a problem if the price becomes volatile because users might decide to change their mind about the purchase and sort of halfway just opt out.