Alts?

So at the moment I'm guessing most people probably have just a single account, but eventually people are going to start wanting multiple accounts. How is this going to work? Only when public signups are allowed or can we use our invitations to invite ourselves in as it is? (since they're specifically allowed in the Terms of Service, but there's currently no way to get them except by invitation)? Are we going to require a certain amount of reputation to allow alts? Or will we introduce a nicknames or "identities" feature on top of a single account?