So far, my BM's and MOH have had 10+ women ask them where I'm registered. The shower invitations were a flat card and a medium sized registry card was included in the envelope. Apparently, guests are opening the envelope, pulling out the invitation, and pitching the envelope without looking for any other items. (sigh)
So just a little note of advice..if you have flat cards, tape your Registry card to the back of the invitation or something, lol.