Sending Facebook invites to a wedding as well as official invites in the mail?

[HIS!]

Why not?

Edit: Wow! What strong opinions you're receiving. ;-) I certainly don't think that a Facebook event should take the place of a formal invitation. However, I also don't think there is anything wrong with using the Facebook event invite as kind of a "save the date" type thing with friends of your age. I was assuming you weren't going to insist that Grandmothers get a Facebook so they could RSVP.

But I do admit I considered the possibility that some of your friends might RSVP via Facebook and those same people might be the ones you have to call because they neglected to return the RSVP card. If they said "Yes" on Facebook, you can always remind them close to the deadline that you have to have a definite answer. Maybe it's not covered on traditional wedding etiquette, but I think it's a novel and possibly helpful idea.