I knew this would happen.
Transport for London reports that since it started taking any old RFID contactless payment card on London's buses last December, just over one person every day complains that the wrong card has been charged for their journey. TfL also says that payment card issuers are getting a similar number of complaints. As I said: I knew this would happen ... but I honestly thought the number of complaints would be way more than a couple a day - based purely on my own fumble-fingered foolishness.
It's not like I'm as bad as those high-flyin' business-types (usually yelling into mobiles as they hop on the bus) who just slam a brick-sized wallet down on the Oyster Card reader and elbow their way up the crowded aisle, rapidly chased by a hassled driver because their payment's not gone through properly. If more than one RFID-enabled card is presented at the reader at the same time, the system doesn't presume to guess which card you might want to pay with, it just refuses to accept payment, so slapping a wallet down filled with an Oyster Card, twelve contactless credit cards, two-hundred quid in reddies, three condoms and a bunch of dog-eared Caffe Nero loyalty cards isn't going to do much. Which is lucky.
On a bus, the problem arises when you try to give the reader a fighting chance by only presenting the half of your wallet that you think might just contain the right payment card (or Oyster Card). And, because I rarely put a card back in the same place I got it from, and I'm generally in a hurry, and I'm more than likely holding a take-out coffee, and there's usually two dozen other people forcing their way onto the bus behind me like an inexorable human lava flow, I'm in no position to think methodically about which card is where. So I guess. And invariably get it wrong. Just before pouring coffee on my shoes. Or someone else's.
But that's just me, apparently. And a couple of other people every day across the whole of London, according to TfL, so it looks like the system's working a treat. So far.