Here's how I would see it:
I'm on vacation somewhere and Customer ABC calls or emails me that they can't run payroll. They get the message that I'm out of the office but being a member of this great 90 Minds group, they can email their question to them. They do and one of you wonderful people says, ""Yes, as a member of 90 Minds, we back each other up when needed. How can I help you?""
You proceed to close their quarter so they can update their payroll and the customer asks, ""How am I going to get billed for this?""
You reply, ""That is up to Therese and Technology Integrators. She will be informed of this incident and will handle it as she sees fit."" Maybe they have a support agreement, maybe they don't. Maybe the incident falls under an agreement, maybe it doesn't.
When I return, I am sincerely grateful and thank whomever, knowing my turn will come to do the same for another member. The only thing I see that could be problematic is if the 'manager' sees that I've apparently gone on a too few many vacations and the group has handled a half dozen incidents for my clients and I have not reciprocated, at which point, shame on me! I'm no longer allowed to post the support link on my out of office replies, etc.
Or you get a @JeffSchwenk incident where it is a 3-hour deal after hours. Jeff bills his customer whatever and collects or not. Again, at some point, Jeff returns the favor. Now if I'm stuck with a handful of these lengthy issues and feel I can no longer participate in the group, I would simply ask to be removed.
Am I oversimplifying this?