If Biomega's Boston folding bike could laugh when somebody tried to steal it, it would. It has an integrated lock and if a thief cuts the wire it becomes unrideable. Even though it's part of the frame, it is repairable.
Beyond this unique anti-theft mechanism it is your typical fold-up bike. The only bad news about the Boston bike? You cannot get it! You can go look at if you want at the San Francisco Museum of Modern Art, just don't try and steal it. Or do, and video tape yourself trying to ride away. [Biomega via Inhabitat]