My (at the time, future) brother-in-law caused us to be held up at the border in Blaine, WA heading into Canada about 10 years ago. A few years prior to that, he had been busted for using a fake ID at a bar to buy booze when he was a minor. Canadian customs were apparently aware of this, and after about an hour of waiting, the border agent said - and this is verbatim - "I'm trying to see if there's a reason this won't let us allow him in, but I'm not finding anything yet."

Our vehicle was searched during that time as well, and about 30 minutes later they finally let all of us enter. Nice to hear we aren't the only folk who have dealt with a similar issue.