Amazon.co.uk sent my brother a DS with about TEN multicoloured pixels. So he sent it back. And blow me if they didn't return the same unit posing as a replacement: still loads of dead pixels. So he gave up and bought it off the high street. Mine was fine first time from Amazon though
Unfortunatly dead pixels are still somewhat normal with lcd screens. One or more are usually deemed acceptible by the factory, depending on the size of the lcd. Cant really notice them though, unless you have an excessive amount.
Dead pixels are becoming less and less comon though over the years.