Becuase recently it was WAY too big with like over 80% of the net hashrate. It is different now, but back then the pool operator was not cooperating by closing registrations at the devs request so Eduffield must have removed it.
Last thing we need is it getting too big again so I say leave it unlisted.
Hi
This is not completely true - 80% happened during the night (at least in my timezone) moreover I was on holidays (see the pool news post) and it was probably caused by some issues on other pools. When I read these messages my pool was between 40% and 50% so I did not see the reason to close registration.
feeleep