According to Credant Technologies, some users are unwittingly advertising the location of their laptop to anyone with a cheap off-the-shelf handheld wireless signal detector.
Apparently one of the global hotspots for this kind of theft is Jamaica, but the crime could easily be committed anywhere else.
Something I wasn’t aware of (and is rather worrying in its own right) is that some notebook PCs can stay awake for up to 30 minutes even after the lid is shut. Quite why this is necessary (unless it’s deliberately set by the user) is a little unclear.
Anyway, the message is clear: turn your Wi-Fi off when you’re not using your laptop to reduce the risk of thieves locating and stealing it.