Question:
How do I backup more than one U3 device without using a differenct email address (account) for each one?

ANSWER:

When you download and install Disk Hero it asks you for USER NAME, PASSWORD and an e-mail address (same one can be used for multiple Disk Hero types of accounts as of version 3.9.8).  Just make sure on the registration screen you enter this data in the 3rd option on the screen - make sure you pull the current software from www.u3.com or www.diskhero.com to do a clean install.