Originally Posted by PhotoJim

I may well not be asked. And I understand that not everyone is asked.

Still, I got CBP stickers in each of our passports at YVR on Saturday without any issue. All I had to do was wait a few minutes for a US CBP agent to be available. When he came to talk to us he'd already applied the stickers.

They shouldn't be necessary, but they might be helpful.

One place where they likely will help is at airports like DEN where there is no GE. Show the CBP sticker, get taken to the front of the line. Without a sticker, you'll appear just like everyone else.