Actually, the surest way to get your data off of a hard drive is to degauss it (magnetically erase it with a degausser machine) because hackers can still retrieve information from pieces of a hard drive. Also, smashing it is bad for the environment and is not a feasible option for large corporations with large quantities of hard drives to destroy.
For more information on degaussers and hard drive destruction check websites like www.protondata.com