Nokia is fairly good about explaining that this is for oversampling/downsampling and in-camera cropping to a more reasonable final output pixel count:
"It’s not about the amount of the pixels, it’s what you do with them. ... It takes every bit of image goodness captured by a 41 MP sensor and Carl Zeiss lens and turns it into beautifully detailed 5 MP photos and Full HD videos." ---
http://europe.nokia.com/pureview"At standard resolutions (2/3, 5 and 8 megapixels) this means the ability to zoom without loss of clarity and capture seven pixels of information, condensing into one pixel for the sharpest images imaginable. At high-resolution (38 megapixel maximum) it means the ability to capture an image, then zoom, reframe, crop and resize afterwards to expose previously unseen levels of details." ---
http://press.nokia.com/2012/02/27/nokia-808-pureview-ushers-in-a-revolution-in-smartphone-imaging/"The large sensor enables pixel oversampling, which will be explained in detail in this paper but in a nutshell it means the combination of many pixels into one perfect pixel." ---
http://europe.nokia.com/PRODUCT_METADATA_0/Products/Phones/8000-series/808/Nokia808PureView_Whitepaper.pdfBut as usual, the marketing people can say some things that make the engineers cringe.
