There has been some debate on channels about 'dimdoorexplorers', people who
run explore (or whatever) through other peoples doors. How about implementing
a feature, cast dimension door at <number>, where number would be the amount
players who can travel through that door after the door closes.
This spell would prevent unwanted people to wander through the rifts of
dimension, but not without a cost (spcost 2x dimdoor or so).