Haha the only place I've ever worried about it has been when I go work in a local library and have to use the bathroom. I ask the person next to me to watch it for a few minutes. And thanks for answering my question about TM backup yesterday!
My initial security step is to just look imposing. Being 6'7" and 260# and using the common sense most Manhattanites have doesn't hurt at all. Nobody's made a wise crack to me in public for 30 years.
Next is the "Protected by Smith & Wesson" sticker on my car's bumper.
It's either with me in my backpack or left at home. Sometimes in my car if I won't be gone long. Usually when I leave school and run some errands before going home.
I had one of those Kensington locks for my 09 MBP when I first went away to college and ended up not using it after my parents dropped me off. I couldn't get it to work right, and I had s drawer in my built in dresser I could padlock if i really didn't want my roommate getting into things.
The workplace, where IT Security requires that all laptops are secured to the desk with a lock. I imagine many workplaces are like that. This is not an unusual situation.