No one should be forced to join any instance, so you are right to think of concerns...But, there are things that can be done to help keep an admin incentivized.

No one should be forced to join any instance, so you are right to think of concerns...But, there are things that can be done to help keep an admin incentivized. For example, if the instance is expected to be run as a community projec,t then admins should committ in a manner that is accepted by the instance community (i guess not so different from open source projects)...Or, maybe have more than a single admin to fend off any single person losing interest...Or, you know, leverage the capitalist mechanism of paying some small fee to a group to help cover hosting, admin fees, etc. I'm sure there are other mechanisms that can be used...Anbd, there's of course the tools to move your stuyff to another instanace anyway...But, yeah, you shoiuld go into this stuff with eyes open - muich like other things on the internet. :-)