If you're a human being, the odds are likely that you've been invited to be a guest at someone's wedding at some point in your years. And if you've experienced both sides of a wedding- i.e. you've been a bride or groom, or a contributing party to the wedding- you likely understand that a guest's reply means much more than just a seat at the reception.
I recently planned a wedding that featured many guests dropping at the last minute, despite their original "will attend" replies. The poor bride ended up frustrated and threw out her plans for assigned tables all together. In discussing this with the catering manager, it became clear that a blog post about guests behaving badly had to happen, and fast.
When you RSVP (Repondez, S'il Vous Plait for all you Frenchies out there), you are not only reserving a chair at a table for the reception, but may also be reserving: a chair cover, a sash, a minimum serving of hors d'oeuvres, a plate of food, a charger plate, a silverware setting rental, a napkin rental, a water glass, a wine glass, a favor, a cake slice, a cake plate and napkin, and, if you happen to be the guest that pushes the table count over into having to provide another guest table, you are also reserving a whole other table, linen, and centerpiece. Doesn't sound so cheap, huh?
Because final head counts are normally required to be to the caterer and/or venue 7-14 days prior, if you decide at the last minute not to attend, the bride and groom will still pay for your spot and everything it took to give you a place setting. This cost, in total, can be anywhere from $50.00/person to hundreds of dollars per person.
So, in conclusion: hopefully you'll think past the just empty seat you'll be leaving if you decide at the last minute not to attend..because in fact you're actually costing the bride and groom more than if you shown up in the first place.