Great idea. We have that actually implemented, but are currently not displaying it. Unfortunately people are even less likely to give a website access to their emails, since this often means giving access to pretty much everything (through "I forgot my password" emails)

Or use this

http://www.amazon.com/gp/help/customer/display.html?nodeId=2...

I know it puts some burden on the customer, but as a fallback, it's better than losing them.