You should be careful before making an offer that your customers can’t pass up¹.

Darden Restaurants Inc. Wednesday said it had replaced the head of Red Lobster, its biggest chain, after an all-you-can-eat crab promotion went awry.

Darden President and Chief Operating Officer Dick Rivera will succeed Edna Morris as president of Red Lobster.

Morris, who had been in that job just 18 months, left to pursue other interests, the company said.

Darden executives said Red Lobster management had badly miscalculated how many times customers would refill their plates after paying $20 for an “endless” crab entree. Meanwhile, crab prices were going up, sending the profit margin crashing.

“It wasn’t the second helping on all-you-can-eat but the third,” said company chairman Joe R. Lee on a conference call.

“And maybe the fourth,” added Rivera.

¹ If you like that sort of thing.  I don’t eat anything that has an exoskeleton, but that’s just my personal hang-up.