I generally hate when people do this. At work or at home, if you're reading my screen while I am doing anything, especially if it is something none of someone's business, the anxiety becomes Mike Fucking Tyson and I lose absolutely everything i was focusing on and am more concentrated on how I am going to ask for it to stop without reciting the last rights and how to stick the fuck off i have for them up the ass.
And I already have massive personal space issues. Get close over the shoulder and doing that shit is how you get your own television show sponsored by the evening news and my name to lone assailant.
Of course way blown of of proportion, but holy fuck. Everyone has that "thing" or a few of 'em.
That is my absolute #1.