Sorry about the hassles you get, but i for one am happy you need to show a credit card to get on board if no one has seen it.

I dont know CO's policy these days but have been stung a few $000 (got it back!) last year when my credit card was used online and via the phone, and they happily allowed e-checkin as well as normal check-in...of course they didnt have to show the card.

Same goes for reward tickets for other people, UA usually require a fax or visit to a CTO before they issue...CO do it over the phone no questions asked, just the good old PIN number. Security?