Evite etiquette

As a recipient and also a distributor of Evite invitations, I've been thinking about proper protocol for responses. Yet, I'm not the only one, as evidenced by a quick Google search. Hey, if the blog from the all mighty Evite tells you to RVSP, RVSP! It only takes a second or two, honestly. Word to the wise: the host[ess] can see if you've looked at the invitation, so don't try and pull that "I never got it!" trick.