Consider this:
1) Spending the same amount of time screening every passenger is less efficient than spending more time on "suspicious" people and less time on grannies and infants, right? (most cops can tell who's "suspicious" and who's not without resorting to a federal checklist and a database)
2) With an ID card that supposedly ensures less screening is necessary, that means grannies, infants, and infrequent flyers will be subjected to more security screening than those with ID cards, right?
Suppose a terrorist gets one of these ID cards. Now you're spending more time screening grannies, infants and infrequent flyers than you are terrorists! Whether you believe profiling is effective, surely you can't argue that spending more time (not the same amount of time, *more* time) screening Grandma makes any sense!
And another thing -- if this special ID card requires an FBI background check, it will take years and years for even half of the airlines' FF members to get checked out. How long have we been waiting for all the airport employees to get background checks now? Imagine doing that for a quarter or half the passengers! This is a stupid idea that WILL NOT WORK!