As to further content issues, I generally try to let things through, even if my authoritarian nature urges otherwise. If I do not forward a message to the list, I will always send the message back to the sender with an explanation why I have not forwarded it. Conference announcements, even those in the U.S., frequently draw international audiences. I would welcome most conference announcements as valuable sources of information - insofar as they have some relationship to the topic of digital libraries. The policy is not to forward messages with attachments.
Attachments cause many problems with different mail systems thus the above policy.
If perchance a message with an attachment gets through, it is my fault and apologies ahead of time. I am reluctant to stop certain messages which I think are somewhat inflammatory. One strategy that I would encourage subscribers to abide by is that responses be directed to the source rather than the list as a whole - unless you feel your response is appropriate to the whole. There have been a large number of bounced messages because of mailboxes being full or the subscriber mail address was no longer valid. This causes more work for your frenzied moderator and contributes to network overload in general.