Dan,
Decision 33-8/2 prohibits putting a ball drop on the far side of a water hazard for a ball which fails to clear the hazard. Even thought it isn't allowed, many clubs do it.
The Teeing Ground is an area that is the width of the tee markers and goes back two club lengths from them. But, there is nothing in the rules that says that area has to be on flat, mown grass. It is common courtesy to provide that much room, but, just as the rules don't specify that the hole must be a certain distance from the edge of a green, they don't say you have to give that much room. Again, I certainly would make sure that at least part of the teeing ground had two club lengths behind the markers on a par 3. On other holes I don't believe it matters that much, but I wouldn't want anything that interfered with a player's backswing to be in reach.