I guess that was a lot less of a problem with IRDA as it required line-of-sight, which limited the abuse potential significantly.

Some devices would even establish an IRDA connection automatically as soon as they found anything. I have friends whose laptop names have suddenly appeared on lecture room projectors, as their laptop's IRDA receiver was in direct line of sight of that of the teacher's.

Not that you couldn't do that with Bluetooth, some early BT chipsets gave you a "<device name> wants to connect to you" dialog box any time somebody tried sending something to your device. This could be abused, to great student amusement, to display funny messages on that same projector if the lecturer's laptop had such a chipset.