The idea was born while interacting with my intramural basketball team. We needed a poll of who was going to be at the game each week. One member created a "group" at one of the many group management sites just so we could send a message and use a poll. With MooGroups, there is no need to signup, no need to manage anything, and you still have access to bells and whistles like polls and attachment archiving.
Also, like with traditional email, MooGroups conversations are in a sense "disposable". You send out a group email about an event this weekend and after that, you forget about it. There's no reason to setup a traditional group contact such as in gmail just for a single email.
With the embedded polls, this extends the usage possibilities invites, opinion feedback, etc.
All feedback welcome!
Thanks -Steel