I was in need to subscribe to mail group hosted by Big Brother using my current mail, and I've found answer here: How can I subscribe to a Google mailing list with a non-Google e-mail address?
Only that it was not the accepted answer, but the answer posted later, because in the meantime the Big B has changed their URLs.
The question is still useful, only the accepted answer is misleading. Generally it is a problem with questions regarding third party web sites or API.
So what should be done with that question? Comment the outdated answer? I've done it. Beg for upvotes on actual answer? Posting on META is a bit of it. Closing as too localized? It would be a pity because Google Groups are really broadly used and that question is useful for a lot of people out there.