yes a u-lock would fit around a punk's neck. I read about a guy who locked himself to a sign in order to avoid getting arrested by cops. They un bolted the sign and hauled both in. CRAZY!!
A guy at work keeps his ny lock on the bike rack and just carries his u-lock around for shorter errands.
good luck with not get you bike stolen! you could also try throwing enya & kenny g cd's at them, its our kryptonite
jeff