If you click on your username in the top right corner of your my.pogoplug.com site, then click settings, you may add an email address to an existing Pogoplug account. Simple click add next to your current email address, and enter your another email.
If the new account is already registered as a Pogoplug user, you must input the password. Click Ok, and the two Pogoplug accounts should be merged.
However, if the email being added has already been entered into our billing flow after having purchased an upgraded account (Pogoplug Family or Team), this merging will not work. The good news is that if one has already upgraded their service, they may simple add users to folders within their account. This option is actually preferable for many of our customers because it allows them to selectively open folders up to access by another email, rather than merging their entire accounts.
Finally, if you add an email to your Pogoplug through the settings option (without Family or Team), the entire contents of your Pogoplug-attached hard drive will be shared to that new email, so make sure that this is what you want before proceeding.