I haven't read all of the preceding posts but for what it's worth, I think that those who don't like weddings and receive invitations should do one of two things.
1. Have the bottle to decline the invitation if it's not your thing, but be consistent. Apply the same respsonse to all such invitations so nobody feels slighted.
2. If you do accept an invitation, even though you really don't want to go, then throw yourself into it and put your best side out for the sake of the bride and groom. It's their day, after all, and you should have the grace to put their feelings first.
The worst thing you could possibly do is accept the invitation and make it plainly obvious, either by your demeanour or by what you say, that you're there under protest. The bride and groom (and their families) deserve beter than this.
This has already been widely discussed. Turning down invitations can cause upset and bad feeling. We have all made the point that we go to great lengths to make out that we are having a great time at weddings. We are, however, allowed to let off steam about them anonymously, which is what we're doing, before putting on a big smile for the next wedding we have to attend.