DEA users are most likely long time internet users who care about their privacy and have learned to protect their email. At the same time, they have enough interest to register and try your stuff - so let them be... If the site requires users to enter an email address for freebies, savvy users will eventually find a way around it, as you suggested. You might also be blocking the early adopters. Eg. bloggers who want to review your stuff, etc!
