That's pretty sad. How rude not to let people know if you're coming or not when an RSVP is asked for.

But, if I was cooking for a get together like that and only 40 people out of 150 rsvp'd, I'd have prepared for maybe 75 to show up instead of 150.
At a casual, outdoor affair if you notice that all of a sudden that there are a LOT more people there than you cooked for you can always run out and get cold salads, precooked chickens, lunch meat trays, etc to fill in any gaps there might be. Been there, done that, no one really noticed or cared.

Hope the wedding was still nice and I can only imagine what one does with that many leftovers(I volunteer to give any leftover cake a good, but temporary, home. Kidding!).

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