I have a FF card for Canadian, which I have never flown, and of course will never fly. I believe I signed up because that was the only way some years ago to even check for fares and seats on their website.
That was stupid, and no wonder a stupid airline went "bye-bye".
Meanwhile, signing up for hotel programs is a good idea, even if you never stay at that chain ever. Because as a member, you can often get upgrades to their "frequent-stayer" floor with complimentary stuff, and special check-in lines. No cost, except for signing up. Good deal.
[This message has been edited by rkkwan (edited Feb 29, 2004).]