Invitations via Facebook

Are regular invitations going away? I got an invitation to a baby shower in the mail and a birthday party invitation via Facebook. Now, personally I don't care how I get invitations--I mean, I'm not 'offended' if someone invites me to a gathering via facebook or email for that matter. However, I do know some people who find that tactless. I'm wondering why that is?

What do you prefer and why?