There should be an age limit for trick-or-treaters. I don't like it when I open the door, look down (about a toddler or child's height) and have to look back up because some fucking 20-year old and his freeloading buddies want some candy. At LEAST wear a costume. Your ugly face won't cut it.
Trick-or-treating door-to-door when you're 18+ is only acceptable if: a) you and everyone with you are totally hammered; b) you are in a college town. Although you should not be drinking before 21 anyway. Plus, I don't live in a college town. So don't come to my door. I'll poison your candy.
Baaaahumbug.