Barack and his BlackBerry

Why is the Secret Service worried about Barack Obama carrying a BlackBerry? The news media hasn't said. They've pretended the question has to do with the Presidential Records Act, or they've quoted Obama alluding to the insecurity of his email.

Neither one of these explanations makes any sense whatsoever. I have a theory: The transmissions of any email PDA or even an ordinary cell phone make it a good locator beacon if you can hack its signal, and these commercial products weren't built for this level of secure use.

You'd think the President is easy to locate - just look for the zillion-car, heavily armed motorcade. But which vehicle is he in? That could really matter, and not in a good way.