I am surprised that I am the only poster that doesn't let them sticker my passport. I used to, but as another poster said, they're gummy.
I decline POLITELY everytime, and have not had an issue because of it. During their surprise phase, I let them know that I'm comfortable if they have to do an extra check at the gate, which calms them down.
But to be honest, it's the same crew at the gate as it was during the pre-check-in interview... so they just waive me on.