So I actually got emails yesterday after my vent telling me that I was wrong, and that it is standard etiquette to be able to bring an uninvited guest. And I was feeling all better after I vented, thinking that I wouldn't have to deal with it again.
Well, for anyone who doubted, here's what the experts say:
http://www.emilypost.com/etiquette/wedding/"Respect your invitation.
Do not ask your host or hostess if you can bring a date or your children. The invitation will be addressed to the people invited. If you may bring a guest, your invitation will read “Mr. John Phelps and guest.” If your children are invited, they will either receive their own personal invitations or their names will be listed under yours on the envelope. This is not the time to question your host’s decision, to argue or to beg for an exception. And, please, do not add their names to a reply card!"
http://www.weddingvendors.com/planning/articles/guest-etiquette/"Return response cards in a timely manner even if you do not plan to attend. Couples must give their caterer an accurate guest count and they need the response cards to do so. Do not assume that your children, a date, or visiting relatives are automatically invited if their names do not appear on the invitation. Many venues, not to mention budgets, are not large enough to accommodate unlimited numbers of guests."
http://www.confetti.co.uk/weddings/advice_ideas/confettiquette/guest_stress.asp "Q: Can I bring a guest to the wedding?
A: To answer this, take a look at your invitation. If the invitation just has your name on it, only you are invited."
Or just go to any search site and type in "wedding etiquette" if you need more proof. These were just the first three sites I got.