Cell phones, headsets, printers, mice, other computers (networking), keyboards, PDAs, lots of things. My laptop has it built in. If you have a use for any of these things, then get it. If not, then don't waste your money.
i wouldn't use bluetooth as a deciding factor. if the laptop you buy happens to have it then it's a bonus but if not don't go out of your way to get one that does. if you find in the future that you need Bluetooth then you can just buy a USB Bluetooth dongle. it really is a fairly useless technology.