[sukilot]

I presume double spends happen often, as people try to trick counterparties who don't wait long enough for transactions to settle. Note that neither branch of a double spend is the "real one" (the feelings of the double spender don't matter), only the future development of the chains picks which is real and which is fake. It's basically equivalent to putting a bank check in one envelope, and another check in another, for a total that overdraws your account, and then sending them out to pay people. It's unknown which payment is invalid, until later.