A similar thing happened in the auto industry. http://en.wikipedia.org/wiki/Vehicle_recycling#Policies
Data leakage via computer disks is a real and potentially very serious problem. It can happen if you send a failed drive back for replacement. It can happen if you take a computer into a PC store for repair and the guy on the help desk starts browsing through your files. It can happen if you take a retired PC for recycling without proper precautions, which you can't always take if you retired it because something failed. This is not a hypothetical risk: all of these things have happened and been publicly reported plenty of times.
If you give someone else your drive after you've stored anything sensitive on it, you're asking for trouble. If you do it as a business that works with sensitive information such as financial or health data, you are almost certainly breaching regulations in a lot of jurisdictions.