Encourage people to turn off their machines.

If we make the service as easy to use as we should, people will make servers and never touch them again.

Since RAM is probably the limiting factor, we need a way to encourage users to turn off machines they aren't using.

Someone suggested emailing users every so often, requiring them to confirm that they are using the machine. This isn't very burdensome and might work, so it seems like a reasonable first approach.