covering 100,000 hard drives-praying for a sign, throwing salt over your shoulder, or visiting a psychic are nearly as reliable as using a SMART utility to predict HD failure;
Also, HEAT and USE do not seem to correlate between a drive failing and one that does not
There are certain parameters on a aggregate scale such as Googles server farms-where these utilities have SOME value-but for an individual consumer-the above suggestions are cheaper-and maybe as reliable
There may be some exceptions-probably based more on luck or coincidence
All in all even a free smart utility is no more than a 'feel good' device-like a rabbits foot
Considering to horror of data loss and the expense of recovery-the manufacturers should simply adjust the QC formula-'the acceptable rate of returns' down to 5% or less-this would not add appreciably to the cost-
as most reviews-of the best HDs i read show a 10% average failure rate-ive been researching into which BU HD might be the best for me- im seeing an UNACCEPTABLE failure rate-conisdering what you buy it for-one should not have to worry
To be safe, your computer and external HD should exist as redunant BUs-VERY unlikely both could fail at once-but I know im tempted to push all overflow stuff onto my BU-but the worry-should I buy a BU for the BU?
http://labs.google.com/papers/disk_failures.pdf

if someone has other data showing differently-please submit