I believe the out-of-sight-out-of-mind theory, but I don't have any evidence to back it up. Maybe it works, and maybe it doesn't. I believe it will probably keep kids from climbing on your bike. It will probably keep adults from sitting on your bike, or messing with it out of curiosity. It might deter an opportunistic thief. I probably won't deter a determined thief.
“There are only three sports: mountain climbing, bull fighting, and motor racing. All the rest are merely games.” — Ernest Hemingway