moderated Re: Samuel's Paid User Proposal #suggestion
In my opinion: no refunds. The site would say that before you pay (we're talking about $2.50 here).
Others have suggested that Groups.io have a generous no-questions-asked refund policy. I'm fine with that too.
Either way, if the member can't have (or doesn't request) a refund then in addition to membership in his/her desired group, the member gets the reassurance that the group owner has no motivation to kick him/her out to make a slot for someone else.
There might be some issue with how people find out that there is now a free slot, there could be a bit of a gold-rush to grab the free slot. Same problem as if there are no paid accounts: people hanging around trying to grab the next available slot.
Maybe there's a waiting list for them, as has been suggested before. If so hopefully such a list could be automated somehow so that the group owner doesn't need to manage it. Maybe it is optionally controlled by owners that want to manage it (select who gets the next slot), otherwise the slots could be filled in the order that people entered the list.