Something goes horribly, horribly wrong with Warhammer Online’s payment system and both existing and ex-players see multiple charges appear on their bank balances. Worse than that, multiple, multiple payments. Payment times ten, times twenty, or even more.
You can release a bad patch, filled with bugs and game changes that everyone hates, but in the end those changes are virtual and may be patched back out. When your payment system goes nuts and starts costing people real money, it completely kills their belief that you can handle their most private details. It tells everyone else who hears the news that they shouldn’t even risk providing their monetary details, just in case you screw up again. Finally, it reminds players to check if they really did cancel that WAR subscription, leading to the loss of easy-money zombie accounts (i.e. accounts that are still paid up, but not used by the player anymore).
Also, on top of refunding the charges, EA / Mythic Entertainment really should pony up the money to cover all of those overdrawn or extra bank fees that have come up due to this mistake, plus they are also open to damages from people who suffer something like not having enough money in their accounts to do things like pay rent or mortgages.
WAR was already swimming against the tide to rebuild player interest and goodwill; this kind of snafu destroys all of that good work and more. Honestly, this error ranks up there in contention as one of the worst mistakes a MMO has ever made.