Granted, my border crossings are extremely limited, so I've never had any trouble. However, my boyfriend and our friend were hassled on the way back into the US from Canada once. Our friend happened to have a full dark beard at the time, and had Egyptian stamps in his passport from having done a study abroad thing a couple of years before. They held them for like 20 minutes while they searched all his bags, but didn't even touch my boyfriend's stuff, and took my boyfriend's word for it which bags were his and which were our friend's. I understand that border crossing guards have a job to do and it can't be a fun one, but sometimes the way things are handled certainly seem a bit fishy.