I think there needs to be a measure of reasonableness here. If I shred a couple dozen documents and dump them in the recycle bin, I think at this point we’re below the threshold of the other identity theft risks previously mentioned (bank employees, HR folks, the mailman, etc).
Using a $60 crosscut shredder to shred old finance documents and credit card solicitations seems like reasonable security for me. I’m not going to lose any sleep worrying about someone digging through my trash and pasting those little bits back together. They’re just going to go down the alley to find the guy who doesn’t shred his documents.