[drewblay]

>there is a large subset of potential users who can not be bothered to sign up for your site via email

There is a simple solution to this. STOP ASKING USERS TO SIGN UP! Do your REALLY need to collect the users e-mail? Do REALLY need them to have an account at all? If you do, then when they register don't ask for their e-mail address if it isn't necessary, or at least make the e-mail address an optional field. Hacker News never asked for my e-mail, because there is no need for them to have it. I probably wouldn't have made an account if it did require an e-mail address.