But there's definitely legal grey areas. Like, if you're on vacation but have a job back home, are you prohibited from answering work emails? Sending a commit from your hotel room? When does it go from doing work on vacation to 'working'?
For that matter, even if I'm attending an event, meeting with customers, talking to press, etc. I think the only place I've ever needed to get a "business visa" is China. I'm guessing there were other cases where I was technically supposed to but no one does.
