You may now register a user directly from the Virtual Terminal by using the "Register As New User" checkbox when placing the order. The new registered user will have the same email as the billing contact.
The user will then receive an email prompting them to set a new password for their account.
Also, if a user with that email already exists, the interface will automomatically ask if you want to update your order to be on behalf of the existing user. Cancelling this dialog will put you back into editing where you can choose to change the billing email or uncheck the registration box.
The interface will not currently perform any email checks when the registration box is unchecked.
If you already have the admin area open you will need to refresh the page in order to use this feature.
Note: This feature will only work if your site is setup with reset password functionality.