Why overwrite a file more than once to securely delete all traces of a file?

Question

Erasing programs such as Eraser recommend overwriting data maybe 36 times.

As I understand it all data is stored on a hard drive as 1s or 0s.

If an overwrite

Answer 1

Daniel Feenberg (an economist at the private National Bureau of Economic Research) claims that the chances of overwritten data being recovered from a modern hard drive amount to "urban legend":

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So theoretically overwriting the file once with zeroes would be sufficent.