Expat@Large has a bizarre tale of buffet-eating in Singapore (at least I think it's Singapore). I would certainly be upset if I left my table for a short while and came back to find a family of seven tourists sitting where I had been. Never happened to me, but if it did I think I'd be tempted to leave immediately, obviously without paying. After all, if they deny that it is your table then how can they give you the bill?
When I was first in Hong Kong (and living in a hotel), I used to go to the buffet once or twice a week, and eat vast mountains of food before staggering back to my room to lie down. That was in the days when I seemed to be able to eat as much as I liked without putting on much weight, which sadly no longer seems to be the case any more (hence my interest in the Atkins diet - not that I have yet started following it).
Buffets in upmarket Hong Kong hotels are quite something, and I don't think I'd ever had anything similar prior to coming here. The problem is that after a few weeks it's easy to get bored with them, because you eventually realize that actually the selection doesn't change that much from day to day. The ubiquitous luxury items such as smoked salmon and oysters are there every day without fail, as are the salad items and the soup, and some form of roast meat (usually beef), plus the vast array of cake-type things.
Do they still have fines in Singapore for people who take food from the buffet but don't eat it? Does that still apply if they have given your table to someone else whilst you were filling up your plate?