Krileon,
Your response seems to be "I can't think of an effective solution, therefore there is no problem."
But, in fact, there is a problem, and here it is:
1. CBSubs is intended to restrict content to paid subscribers.
2. People other than paid subscribers can easily access the "protected" content via complicity of a paid subscriber who provides the freeloader with his username and password.
3. The complicit paid subscriber and the freeloader can then log in at the same time with neither suffering any adverse performance consequences.
4. Ergo, there is a loophole in the system. CBSubs attempts to restrict access to content but does not address the most basic means of bypassing those restrictions: multiple simultaneous logins with a legitimate paid subscription.
Perhaps one additional factor I should mention is that in my particular application, the subscribers have opportunities for actual face-to-face relationships rather than just online relationships. Obviously, this greatly enhances the likelihood of collusion (a/k/a petty larceny).
What are my options? Stare at the "Who's Online" panel of the Admin, watch for multiple logins and then deal individually with offending users?
You're a smart guy. I bet you can figure something out if you put your mind to it. But, as usual, the first step is admitting that there is a problem.
And, certainly, from my point of view as a guy who counts on paid subscriptions, there is.