(quoted manually, please excuse typo's)
Under the illusion that they'll have complete protection, many people burn floppy or hard disks, crush and mangle them, cut them into pieces, pour acid on them, and otherwise physically manhandle them so there's no way they could ever be used by another computer again.
Unfortunately, physical destruction of floppy and hard disks still can't guarantee that your data will be safe since goverment agencies such as the FBI and CIA practice a specialized technique known as disk splicing.
With disk splicing, someone physically rearranges the pices of a floppy or hard disk as close as possible to its original condition. Then they use magnetic sensors or electron microscopes to scan for traces of information still stored on the hard drive.