The Server Properties window has several options that relate directly to Guest accounts. One handy feature is you can restrict the total number of guest accounts that are logged in at any given time. This is important if you have accounts that don't have the "In reserved list" right assigned to them. Its can also be useful if you run a public server and want to prevent the trouble makers from hijacking your server.

You can also enforce a time limit that a guest account can remain connected in addition to specifying an automatic timed ban preventing that guest account from coming back into your server.