"rsvp-etiquette" news and stories

This weekend, I'm hosting a casual dinner reception following a friend's fiction reading. In the past, I've used Evite and Facebook to create invitations, but the number of responses has been increasingly dismal, so I tried sending an email this time. Out of 40 invitees, only 11 have RSVP'd so far, despite a special request for replies so that I would know how much food to cook.

As a frequent hostess, I find this to be one of the most annoying side effects of the digital age. It's easier to RSVP by email or Facebook than by phone or snail mail, yet most people don't bother. Yet it's still just as wasteful to buy and cook food that nobody eats, and just as embarrassing to run out if extra people show up.

What's a hostess to do? Do I simply delete the incommunicado among my acquaintance from future guest lists? Send nagging emails? Or must I switch back to paper invites if I want to guarantee a courteous reply? Also, I'd be interested to know whether others face this issue, or whether my friends just happen to be particularly ill-mannered.