from NetworkingGroups

Why use an online service like Yahoo Groups instead of a personal mailing list?

• Easy group management. It's a painful manual process to copy, paste, and delete addresses into a group email list, especially if you have a lot of members. An online service automates list adds and deletes.
• Group discussions. A personal list works only for outgoing announcements only. It's not suitable for member discussions. With an online group any member (or anyone else, depending on the settings) can send group messages via the group address, by replying to a group message, or from the group web site. Email also doesn't handle discussion threads, aside from marking past messages. Groups typically do.
• Don't be the weakest link. A web-based service is always accessible. If you have a personal list, you become the bottleneck. The group is unreachable to others if you're on vacation, travelling, or busy. A web service enables multiple moderators. Other members can approve new messages and members. They can share the group management load or take it over if you're not available.
• Archive. Online groups archive messages so it's easy to see past messages and threads.
• Additional features. Online groups provide useful features that go beyond email like a calendar, polls, file storage, etc., as well as a variety of message and member settings.