How paperless can you go?

I can't blame you if you thought that my promise of a post even obliquely related to productivity would go unfulfilled for a while, but here I am with offering number one.

I'm a huge packrat. I hang onto souvenirs, I keep product packaging, and I hoard paperwork. I still have the receipts for every single credit card purchase I've made since July 1997. As you can imagine, a large portion of my household expenses involve storage and shelving of one kind or another.

There's been some talk recently in the blogosphere about "going paperless" with your personal finances, and this idea really appeals to me. Some simple steps, such as opting for paperless record keeping from financial institutions, are virtual no-brainers. Why receive and keep paper statements for something that you can track in real-time online? I'm already paperless on my primary bank accounts, and am working to convert the rest of my relationships to paperless.

The idea of digitizing paperwork using a scanner is very interesting. Storing paperwork as PDFs seems like a really slick and elegant alternative to keeping stacks of physical paperwork around. However, I'm not sure to what extent one can rely on electronic copies of paper documents. Will stores accept scanned receipts as proof of purchase when making a return or exchange? Some documents, like stock certificates, deeds, etc. obviously need to be kept in their original paper format, but can recent tax returns be converted to electronic documents?

Where's the line between what can be stored digitally and what must exist as a physical original?