Worst is someone in a new executive type car, which you know will have an in-built car kit, yet they still hold the phone to their ear. Maybe it looks cool (to them). Our cars have factory fitted phone kits.
Only problem we had was once Rose came home and drove into the garage which my office is above, my conference call switched from my mobile to her car... she suddenly got a conversation with a bunch of foreigners about something she knew nothing about! Took me a moment to realise what had happened and switch off my phone's bluetooth!