The majority of my family, including myself, uses Dropbox and Syncplicity free accounts for our syncing needs. However our backup strategy is pretty non-existent, we all have access (via webDav) to our qnap nas located at home, however we copy files accross when we can remember to do so, terrible I know.

Is there tools like CrashPlan or Spideroak that allows each the accomodation of each family members syncing and back-up needs under one main account? I'm not sure how this would work, as each family member would need a seperate sub-account or would I manage each computer's syncing and backup lists from a single account? Any thoughts?