It's a ubiquitous part of American life. Here's a recent example from Los Angeles:
David Martin was in the mood for raw fish, and he liked the deal offered by a Studio City sushi restaurant: all you can eat for $28. He took a seat at the counter and started ordering. But it turned out that Martin didn't really want sushi, which includes rice; he wanted all-you-can-eat sashimi, which is just fish. He began picking the seafood off the top and leaving the rice. Restaurant owner Jay Oh told Martin that if he wanted the all-you-can-eat price, he'd have to eat the rice too and not just fill up on fish. Martin replied that he has diabetes and that he can't eat rice.
Oh said he offered to prepare sashimi for Martin. Two orders of sashimi cost $25, or $3 less than the all-you-can-eat sushi deal. But Oh said Martin declined the offer. Martin left the restaurant after being charged a la carte prices for the sushi he'd already ordered plus $1 for a cup of green tea. Two weeks later, Martin filed suit in Los Angeles County Superior Court. It seeks at least $4,000 in damages for the "humiliation, embarrassment and mental anguish" Martin says he suffered after being discriminated against "on the basis of his disability."
David Lazarus, himself a diabetic, explains why this is bunk.