Some mailing lists come with a negative service level agreement, but that's okay, because everybody is in on the joke
As I noted some time ago, there’s a mailing list devoted to chatting among people who work in a particular cluster of buildings. It’s not a technical support mailing list, but people will often ask a technical question on the off chance that somebody can help, in the same way that you might ask your friends for some help with something. Of course, one consequence of this is that the quality of the responses is highly variable. While there’s a good chance that somebody will help you with your problem, there’s also a good chance that a technical question will receive a highly unhelpful response just for fun, in the same way your friend might respond to a question with a funny but unhelpful answer. (And there’s also a good chance that a technical question will get both types of replies.) You don’t complain about this because, well, that’s what you sort of expect when you use this mailing list.
An illustration of this principle comes from the following thread:
When I do ABC, I get XYZ. How do I get DEF?
A short while later, the same person replied to his own question.
Nevermind. I found the right mailing list to ask this question.
That didn’t stop somebody from responding:
This mailing list is the correct place to send all questions. You have to use a different mailing list to get answers, though.