It's all about marketing. More MP = better = more sales.

Canon did listen and actually lowered pixel density for their newer S and G series from 14.7MP (G10) to 10MP (G11). Great move. Wish they lowered it to like 6MP and take full advantage of the improved technology in both sensor and processing to create a DSLR rivaling clean images at ISO 100-800 range. (and allow it to have useable images up to ISO3200 or so)

Have you seen the very first 3MP Foveon sensor'ed SD9 pics? If you haven't, I recommend you to check it out. It was crap above ISO400 or so but at ISO100, it is just amazing. That's what I want from my mobile phone. Beautiful crisp 3MP images. Not over-processed 10+MP images. Just check out the full sized image of the very first pic of Phil's wife. What an amazing picture quality. This was 8 years ago! (the sensor does have its flaws but was a great technical demonstration of what a true rgb sensor could achive at a pixel by pixel level)

http://www.dpreview.com/galleries/re...ples/slideshow