The linuxham group is one that as received as many as 30 bogus subscription requests a day. This is a group dedicated to amateur radio and I simply reject or ban any request that does not identify the amateur call sign. The membership never sees these requests, but they do add to the work load of volunteer list moderators. I would be in favor of subscription confirmations. Make sure that the confirmation is not one that is easily spoofed by a robot.
I would also suggest that a single IP address subscribing to several groups in a time window be automatically flagged and banned.
