Today, I was in a camera store looking at some products and someone brought up the number of pixels between the Nikon D800 and the D4. The D4 and its predecessors have concentrated on speed and image quality, while the D800/D800E and its predecessor concentrated on pixels.
This person mentioned something about most people not being able to understand about why pushing too many pixels onto a sensor didn't make sense. I explained it to them, as I've been doing since 2004: When you crowd more people onto a bus, you end up with a bunch of angry riders, and they become noisy. Putting the same number of riders onto a smaller bus does not make for happier people, and you should see even more noise, all things being equal. They asked to borrow that.
These days, we have buses with better seating capacity and more athletic riders, so we can have more pixels from that same sensor size with reduced noise.
Now, I hope people will remember that it was my analogy and not everyone else's.