Perhaps it's just my 'honest' face, but I've never even had a customs agent ask me any questions, nor stop me in any way. I've made 7 overseas trips in the past year and have just handed over my customs form and been waved on my way! It could be that I only take a small carry on and they must figure I couldn't be concealing anything in there--or the fact that my total dollars spent never exceeds $100.00.
Watch, now that I've said this I'll get a full search next time out!