I prefer a model where I as owner pay for the service and figure out myself how to pay for the service.
I agree as long as the members limit is lifted or a more affordable pricing introduced.
My group is in the range of 2100 members, at the moment using 29 MB total storage out of 1GB.
I am very thankful to Mark for all the brilliant work and for considering us legacy.
I can envisage raising (or paying myself) something around 200 USD yearly, but anything over that would simply and sadly mean leaving GIO.
I can't surely see myself breaking my head over slots and who can or cannot join my group based on his/her paid membership.
Last but not least, I agree with Catlady when she says:
"I don't think it's reasonable (and/or profitable?) to expect millions of group members to understand and deal with something complicated."
I respectfully wish to remind that GIO has an international membership. We may be a small minority, but not all my members have a good command of English, which makes complicated things even more complicated.
My 2 euro cents,