Apparently it won't be, since some people here seem to think stealing from its users is a commendable practice.
Seriously, how would you handle the case "someone sends an unconfirmed TX right before the bet ends, TX confirms after the bet has been decided" ?
Refund?
You want to discourage scammers, not have to guess every time whether the request is legitimate or not.
Yes, refund minus some fee for the inconvenience. I don't see how it's scamming if the bet is at all in question when the transaction was made. If the price is at $749, is it a scam to bet that it will hit $750? What about $740? $700?
It's very simple as I see it, don't count bets that confirm after the bet is over. That way nobody can cheat the system. If someone tries to make a late bet and the transaction doesn't confirm, return the money minus a small fee. That money is not yours to keep, it's not yours at all. And in situations like the one OP bet in, price can move VERY fast and confirmations can take 30 minutes+ even with a generous fee sometimes. In fact I was watching the price that day and I wouldn't be surprised if the price on the exchanges went from ~$700 or so to $750 in a matter of minutes.