Also not mentioned: Visas and permits. Not allowing it for a "relatively small amount of time" means that you aren't encouraging your employees to go to a count

Also not mentioned: Visas and permits. Not allowing it for a "relatively small amount of time" means that you aren't encouraging your employees to go to a country on "vacation" and working through it, all while being on a tourist visa that doesn't actually allow you to work while you are visiting. This is a pretty common rule for a tourist visa. The things others have said are valid as well.