Atkins Nutritionals Inc. failed because of increased competition. Today, there is a plethora of carb conscious products out there and the Atkins stuff is on the expensive end of the scale. They lost their virtual monopoly and weren't able to respond well.
For a short while there was a lot of low carb products available and it was great. But all of a sudden all the stores just stopped stocking them.
Not to mention that most of it sucks. (I'll make an exception for the Advantage bars and shakes.) Ever try Atkins "pasta"? Yeeeeeechhhhhh!!! I'd rather eat the box it came in. On the other hand, now you can go with Dreamfields, which is made with real semolina flour, looks, acts, and tastes like real pasta, but is manufactured in such a way as to make most of the carbs non-digestable.