The other nifty thing about the plasma globe is that immediately after someone plugs it in, they are likely to be too distracted by the luminous fingers of writhing plasma to notice the shell window popping up briefly on the monitor. Nicely-executed hack on multiple levels.
For the same reason, waiting a few minutes to pop up the shell, as the article says they did, actually seems counterproductive. It might have been better to pop up the window intentionally -- launch the browser to display an ad from the company that made the gadget, maybe, or a 'user's manual', or something like that. Something that would appear innocuous and expected, while providing cover for the payload.