Keeping mailing lists spam free is really annoying and requires a substantial effort nowadays.
At Yahoo Groups, not only is it a common occurrence for a new random-letter Yahoo account to subscribe and fire off a few messages, today a newly subcsribed account uploaded spam files to the file area. WTF!?!
On one list I moderate all new members' messages and flag them as non-moderated if they aren't Yahoo addresses, another list is set up so I need to approve all subscriptions.
It's all so tiresome... *sigh* give it a rest already!