Google Groups invite annoyances

Bit annoyed with Google Groups today, after it completely mangled my attempts to set up a mailing list. I sent invite emails to 20 people, but the acceptance link only worked for 5 or 6 of them – everybody else gets “You cannot view the group’s content or participate in the group because you are not currently a member”, then demands they set up an account – something I explicitly told them they didn’t have to do. Irritating. I directly added everyone’s email addresses to the list in the end, after sending out apologetic and explanatory emails, which isn’t ideal. Hmph.