Re: Bet they all use smartphones though...
I was working at a customer's office, and I was sent to go fix something (Outlook maybe?) on the PC of the marketing manager.
As I started, I found that the mouse was behaving really strangely, so I picked it up, and taped underneath was a 2p coin. (From the sellotape marks it had clearly been positioned over the sensor at first, and then moved). I removed it, and left the coin by the monitor. Presumably it was there because it was supposedly made of copper?
Once everything was fixed, I was just waiting for the user to get back, and they eventually turned up, mobile phone glued to their ear. Once they finished their conversation, I pointed out that their mouse wasn't working because of a coin to which the reply was "but you see, I'm allergic to electromagnetic radiation".
"Well then" I replied, "maybe you should try shutting the curtains".
I don't think they figured it out by the time I left.