I've never known a game as scarce as Mario Kart. Its been an utter utter bastard to get hold of for about two months now.
To be fair, and I will be fair, I've not looked for it much (or at all). All I know is that whilst I was awaiting my pre-order, I was in a local Argos and the little stock machine thing (anyone remember the hell that Argos was before they arrived?) said they had 20. I considered buying 1 'just in case' but then thought 'nah' which was a stoopid mistake.