They don't use those media for one-to-many invites, though. Sure, my friends could email me everything they post to fb, but they don't - everyone else is already there and gets it.
You can poll your friends. It can work. I have a couple friends without Facebook accounts, they are not anti-social. Perhaps introverted. Sometimes we have to remember to tell them about events. Personally though, the invites and private messaging are what I like most. I think it's just great not having to know somebody's phone number or email address.