You have to pair the device with a given computer. It's not like somebody could just walk into your computer area and turn on a bluetooth mouse and have control of your mouse movement. The computer and the device both have to be introduced to each other first.
Bluetooth chip has software controls and identity coding to make sure it works only with the device you pair. As per avoiding interaction with other radio devices, it uses frequency hopping.
cheers
So it would be theoretically possible to set up a computer lab using 50+ computers in the same room all using BT mice?
Too bad wireless mice would have a greater tendency to find their way into pockets. It would be really cool to have a bunch of FP iMacs with wireless Apple keyboards and mice. Very minimalistic.
I can't wait to see where wireless technology is in 10 years. Imagine a compact HD that you just carry in your shirt pocket that you can sync up with any computer you sit down at! Future of the iPod?!?