I've not had this happen often, but I don't feel comfortable with it. Especially in today's world. I'd never, ever agree to do it in an airport, for example.

I'm not paranoid, but I am wary of strangers. I'm more than fine with watching a friend's purse if we are meeting for coffee and she needs the restroom. Strangers....not the same fo me. I have had men ask me to watch their laptops in cafes and it was pretty clear they were using it as an excuse to hit on me/flirt. I'm not interested.