The biggest headache when you invite people to a wedding comes during the RSVP 'cos the RSVP etiquette is seriously missing among Malaysians. Only 25% of our guests bothered to confirm their attendance before the RSVP deadline.
The worst culprits are relatives. I suppose most of them think that an RSVP is unnecessary simply because it is assumed that they would be attending without considering the fact that we have to know the number of people coming along for the party.
The deadline for our RSVP was last Sunday and, after numerous smses and phone calls the past 3 days, we still have 6 invitations without RSVP and one tentative (subject to leave approval so considered excusable).
I really don't know how people manage huge weddings that run to thousands of guests.