Quoting Michael Paoli (Michael.Paoli@cal.berkeley.edu):
To cover it yet a bit more fully :-) ... could also tweak the text in the confirmation email, and on the confirmation web page. That'd cover it yet more fully. And yes, some folks will still be idiots, and not read what they're doing or agreeing to.
Likewise could also add the information to the BALUG-Announce unsubscribe information.
Which would not actually address the fundamental problem.
Nearly 10 years the policy has been in place, over 800 subscribers, and thus far hasn't been an issue.
Well, I wish BALUG continued good luck.
Me, I'd not feel ethically right, doing that.