[CRConrad]

But if you even notice the (thin, dark?) bit of cord between a guy's wrist and laptop computer when he's working on it at a table in the library, wouldn't your first assumption be that he's a bit paranoid about having it stolen and therefore has strapped it to himself by the Kensington Lock slot? So you'd be quite OK with stretching it as far as it goes -- only noticing later that in this case you could "stretch" it beyond that, popping out the USB connector. (Actually, wouldn't a lot of people in a position to do this be only too happy to give it an extra forceful yank, just to hurt the Eevul Hacker?)