I always wonder if my helmet will be on my bike when I get back. I've heard stories of helmets being cut off from bikes that lock them on (yano, the expensive Shoei helmets). Luckily, IL doesnt have a helmet law in case some scumbag steals mine. And the helmet only cost $50 or so. So it aint the worst thing in the world if it gets stolen.
Although I gotta wonder what theyre gonna think when they take a whiff of the inside...
Around here we don't have a helmet law, so I feel pretty safe in leaving my $55 helmet on the bike, along with my $8 gloves, and $4 sunglasses. In all my 45 years, I've never lost anything off my bike, but there is always a first time I suppose.