i'm not sure i could be comfortable with myself if i refused to give up a five dollar bill because i didn't trust the homeless man to spend it the way i saw fit. Just because he MIGHT misuse it (according you you anyhow) is no reason to deny some change to a person who really does need it and will use it how you'd like them to.
now if you'll excuse me, i'll have a lot of catching up to do. someone back in fifth grade never gave me my pen back after a test. I need to get busy stockpiling pens and refusing to loan them out to people who don't have anything to write with in class.