I'm sure this doesn't happen very often, or shouldn't anyway. In places like Denver and EWR, it almost can't since you're greeted before a ride up an escalator. In LAX, PDX, SEA and SFO I walked right in without showing my card and no one whispered a peep. Though I would never try to be dishonest about these things (really!) I do like to know what the limits are.
It started when I walked into SFO RCC and waited in line to show my card and no one looked up. I waited for several minutes, but they seemed preoccupied by something on their compurters. So I just walked in.
I'd let anyone in as a guest if they asked no probs. Just as long as they'd buy me a Sam Adams!
------------------
Where ever you end up, that's where you end up ending up