Of course it is up to Robbie and Jody, but I think charging a mandatory
fee for MMD is a poor idea.
If that were done, then an implied contractual arrangement with the
subscriber would be created. Everyone would want to "get their money's
worth", and that would be defined differently by each subscriber.
Everyone would have different ideas as to how MMD should be done, and
expect their suggestions to be followed. If someone's submission was
edited in a way that did not please the author, then that author could
demand that it be corrected.
The result would be endless discussion and fiery e-mails flying back
and forth, and lots of extra trouble for Robbie and Jody.
Currently people take MMD as it is, or leave it. Of course those
who like MMD should contribute their bit, as I do. But the cost of
e-mailing it to those who don't must be trivial. Leave it as it is,
all for serious fun -- the best free site on the web.