
I signed up for 
Mozy backup in February.  It is now two months later and I have not had even ONE successful backup.  I am just done with it.  I am not even sure if I have successfully canceled my account since their online information doesn't even matchup with their own documentation. Despite my frustration, I will try to explain the main issue:  My backup would stop without any error message.  The best I could get from the support staff is that there is a connection issue.  For awhile, it was their issue but even after it was fixed, it still happened.  So I spent a lot of time sending emails back and forth and almost any directions given by support didn't match up with what I was able to access using their downloaded software.  My suspicion is that support was using a PC while I have a Mac BUT if you offer the service for both, than provide proper support for both.
Since I still think doing an online backup is just a really smart idea, I am going to try a different service, 
Backblaze, which was mentioned by 
Eastman's genealogy blog.  Right off there is one big difference.  You receive a 15 day free trial, unlimited backup.  So I am currently doing a backup to test out the backup process.  Another plus about Backblaze is that some of their team members are former Apple employees.  This gives me hope since I believe that once an Apple user, always an Apple user!