Brilliant! In fact - it's probably more secure than a normal password scheme! No password hash database to be stolen, no brute force attacks to dodge, no chanc

Brilliant! In fact - it's probably more secure than a normal password scheme! No password hash database to be stolen, no brute force attacks to dodge, no chance of your account being compromised without noticing because you'll get an email if someone tries anything (assuming the cookie is safe and SSL'ed)