It is a necessity to have an online backup for your computer files. An external hard disk may serve the purpose to an extent. What if your computer was completely destroyed by natural calamities or fire? This is very alarming in the recent years. All your precious data would be lost with no way to retrieve them.
To be on the safe side, it is advisable to have an online backup for atleast your important computer data files.
One of the recommended source is MozyHome free edition which offers upto 2 GB online backup.