I have. I am forever losing, cancelling or replacing credit cards so I had absolutely no idea what card I had used to book the tickets. I explained that I had almost certainly cancelled the card since then (it was a 241 ticket to SYD, so probably booked 12 months in advance). It took the check-in agent about 45 mins to finally check me in, despite the fact that she had not seen the card. So I really don't know what the point is - they let you check in even without it anyway. Although I am pretty sure I remember someone saying that they had been refused boarding for an Iberia flight for exactly this reason.