Outstanding answer by Mlsstl, IMO.
A key point that is often overlooked by those relying on the cloud for backup purposes is that although the upload processes may go fine if done incrementally, little by little over time, if and when all of that data ever has to be downloaded in its entirety (due to failure of a local hard drive), it may take an absurd amount of time.
For example, downloading 1 TB of data over a 5 mbps connection will take AT LEAST 500 hours. And perhaps considerably more, depending on the speed and loading of the server at the other end.
And if the upload process is intended to be done all at once, rather than incrementally, the number of hours required would extend into the thousands at that connection speed, since upload speeds are generally much slower than download speeds.
Regards,
-- Al