Bosox, I agree. People can and do abuse the kindness of others. However, unless I've seen the specific person before, I'll give them the benefit of the doubt.

I think the message I'd want to send to my children, I dont have any(That I know of )
would be "be kind to thy fellow person" as opposed to "cheaters never prosper".

One time I was connecting in (I think) MSP and the person in front of me was very rude to the gate agent. About 10 mins later, I'm checking into the NW worldclub. Who's in front of me? you guessed it. Only he his membership card has expired. Now if he was nice to the gate agent, I might have invited him in as a guest, but since he was rude to her, I let the idiot pay.

Also, see the following thread from about a year ago, I had another run in with a jerk, boy I must attract these sorts
http://www.flyertalk.com/forum/Forum1/HTML/001821.html