I thought about not doing response cards, but then I thought about all the people who wouldn't RSVP unless they were provided with a response card and a postage-paid envelope (mostly my MIL's tacky friends

) and how much time we'd have to spend on the phone tracking them down...
Last summer, I attended a wedding where we were asked to RSVP by email. This was because the wedding was planned over the span of six weeks, and the invitations didn't get mailed until about two weeks before the wedding. I am convinced that they didn't read the RSVP's at all, because (a) about 1/3 of the table cards weren't picked up and about 1/3 of the seats at the reception were empty, indicating that they assumed people were coming even if they had RSVP'd no or failed to reply; and (b) they RAN OUT OF FOOD with at least 1/4 of the guests unfed! (Imagine if all the people they'd assumed were coming had actually showed up!)