A feature that one of my users has requested is a way to send one message to multiple recipients. A comma separated list would probably suffice for this as I realize you'd have to check each nick to see if it was registered, but it should be slightly less bandwidth intensive than sending the same message several times each to a different person. I wouldn't, however, allow channels to be included in the multiple sending because that would be to easy to abuse.
I realize that this functionality sort of already exists via sending a channel message. But there is a lot of leg work to make this happen because you had to add the people to a certain level in a channel. And the memo only really exists on the channel and not for the person.