ping "Hey, Bob, can I share my desktop and show you something?" Five minutes later, Bob is fixing his mistake. Or, Bob has notifications turned off, and he lets me know as soon as he's available again.

My point is that the tools are there to address this concern. I don't go a day without sharing my desktop or looking at someone else's. And in some ways it's even more efficient and less disruptive than getting up, walking over to someone's desk.