The current encryption scheme implemented by Maven avoids the use of cleartext passwords on local files by allowing them to be encrypted locally and decrypted just before the maven client requests from or deploys to a central artifact repository.
I would like to suggest that the Maven team replicate the idea adopted by Artifactory, where passwords are transmitted encrypted, and only decrypted on the server side by the repository. Requests and deployments are made over http and transmitted in the clear. Where the passwords are system passwords integrated to Active Directory or similar using LDAP, this is not an option even within a company's LAN. I like the idea of where Nexus and the Maven development stack in general is going (I listened to Jason's seminar recently and I'm keen on much of where you are going). But passwords in the clear over http is a showstopper and I'm surprised you haven't already borrowed this idea from the competition.
Another irritating side effect of maven's insistence in using cleartext passwords has been mentioned by a colleague of mine in
MNG-4611. We currently use Artifactory for EXACTLY this reason (the password encryption) and maven logs loudly about the fact that the passwords are encrypted.