There's a school of thought, to which I mildly subscribe, that six megapixels is easily enough for most needs. (Google "6 megapixels" and have a look at some of the articles.) The truth is, a well-taken photo out of a six megapixel camera can be printed to just about any size, for just about any purpose. In the early days of digital, pros had 3MP cameras, and printed billboards from them.
If you really nail your composition, lighting, focus, etc, you can produce a masterpiece from a 6MP camera. On the flip side, if you mess up a shot, all the pixels in the world won't save you - it's still a messed-up shot. It's simply a messed up shot that's wasting more space on your card.
Of course, you can't find 6MP DSLRs any more. There's nothing below 10MP, and plenty pushing 20MP and beyond. And I think this is an appalling state of affairs.
Can you imagine, for a moment, what would have happened if camera manufacturers hadn't devoted so much R&D to putting more pixels on their cameras' sensors; but instead concentrated on making the quality output of the pixels better?
It's only been in the last year or so (with the release of the 5DII and the D700) that great strides have been made in image quality at high ISOs. In my opinion, the years between the beginning of this decade (when 6MP DSLRs were first released) and the end of the decade (when ISO advancements have been made) have been miserably wasted. If the manufacturers had forgotten about the number of pixels, and focused on their quality, we might now have cameras that would be utterly noise free, even at incredibly high ISOs. That would be wonderful.
But it's all marketing, isn't it? Bigger numbers sell more units. I'm sure there are plenty of us who yearn for Canon to release a camera with the capacity of the 10D, but the IQ of the 5DII (how good would that be???) but it ain't gonna happen. Because most cashed-up enthusiasts think that more pixels must be better; and Canon wants to take those people's money.