Get ready to have a bunch of passive-aggressive conversations with your friends, because Facebook is adding read receipts to its events.
It seems like Facebook has gotten wise to the fact that almost everybody ignores Facebook events. First there were the notifications that claimed "You have 7 events today" when in fact I was invited to six different Monday night improv comedy shows and one dog birthday party.* And now the site is working on adding read receipts to private events, so the creator of an event can see that you looked at the event, but didn't respond Yes, Maybe, or No.
Generally, I believe that RSVPing to events is the Right Thing To Do. It's a pain in the butt to plan something like a birthday party, buy enough drinks for the people who RSVPed, and then have 15 other yahoos show up. But the way to get people to RSVP isn't to spy on whether or not your friends have viewed the invite, so you can then a) bother them for not responding or b) harbor resentment and silently judge them.** Besides the fact that there are a whole bunch of good reasons why someone would look at an invite and not RSVP immediately. For example, they might need to talk to their significant other about what their excuse for not attending your dumb party is.