There seems to be a distinct divide on this subject between ourselves & our esteemed Australian cousins. The Super League has it, the NRL doesn't; the Premier League has it, the A League doesn't; the Zurich Premiership has it, Super 14 doesn't; our County Championship has it, the Pura Cup doesn't (although with only 6 states that's perhaps more understandable!) &, obviously, the AFL is ring-fenced too.
I'm interested to know whether people think relegation is healthy for a sport or if the ring-fencing of the top echelon in any sport improves quality? To take League as an example, there's little doubt that the overall quality of the NRL is higher than the ESL, but with it being franchise-based great old names like North Sydney & Western Suburbs have no immediate prospect of a return to the top flight. When the Super League was first proposed over here there was talk of merging several clubs, which the fans violently opposed, even if it meant their club being out of the ESL (Widnes & Hull KR both missed out).