At best — when derived with care — the requirements might reflect what users want. More commonly, however, they reflect the desires of user “representatives” who are too far removed from the coalface to know the details of the real work. In any case, what users want and what users need are two different things, which is why it’s long been a primary usability guideline to watch what users do, rather than listen to what they say.
The only thing worse than having developers deviate from the design specs is having developers implement the design specs to the letter.
A long time ago, I used to read Jakob Nielsen’s alertbox every fortnight – his utterly self-confident didacticism had a curious appeal back when all too many people thought the blink tag was pretty cool. But it’s hard to stay fresh and keep sounding original when you have been writing on the same topics for as long as he has, and I for one haven’t been reading him regularly for quite a while. But he can still come up with some gems, and this recent piece on the possible tensions between agile development and usability design is well worth a look.