To the person who downvoted the parent post: Maybe it's different where you are, but here in the UK the recycling centres typically get rights to do just about anything they want with gear you leave there. For things like laptops that are still in working order, they may literally just wipe the disk and sell it on in another part of the world where it would seem like much more advanced technology. Unfortunately there have been numerous reports of that wiping not being done properly, and things like spreadsheets full of bank details and confidential employment records have turned up on computers in Africa. This happens often enough that I've even seen TV documentaries made about it.

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.