That's right. If you have a camera with a sensor that captures more than 4 to 6 megapixels, you probably don't need them all, and would almost certainly benefit from spending the money on better optics or electronics. My Nikon D50 is a 6-megapixel DSLR, and I don't even always use it at maximum resolution.
Then again, there are people for whom spending $8000 USD on the new crazy crazy 21-megapixel (!) Canon EOS 1-Ds Mark III will be worthwhile. I just don't know any of them.
LATER UPDATE: Hell has frozen over and Nikon has released a full frame DSLR, the new D3. It's smart enough to scale down its sensor resolution if you attach a DX-format non-full-frame lens, which is an interesting compromise. At full frame it only has a little over half the pixels of the Canon 1-Ds Mark III, but it also costs $5000 USD, a little over half the price. So does it reinforce my point? Hard to say. I didn't think I'd see Nikon do this, though.