This is working for my family.
I do have an account for my pogoplug. I can access every file.
On my second hard drive I created a folder for each family member. I shared each folder to one email adress. Every family member created a pogoplug account with the email sent during the share-folder action.
Then they installed the small windows client. Logged in and activated active copy on their folders choosing the shared pogoplug folder as destination.