In-N-Out has the highest profit per location and one of the highest employee retention rates of any fast food restaurant. Their ability to expand is limited more by their refusal to ever freeze their ingredients than anything else (they must stay within X distance of their cattle ranches).

Its a really impressive company, and one that I think backs up Jason's point. There was an amazing article on them recently that I'm struggling to find, if someone has the link and could post it that would be great (BusinessWeek?).