Originally Posted by thiussat
Until someone can provide even one example of someone recovering meaningful data that has been overwritten, I will continue to do one pass.
Maybe on one of those ancient Seagate drives from the 80's that are still kicking around. You definitely need the voodoo to erase those.
Otherwise, it's utterly pointless. Though as one of the very few anti-voodoo people on this forum, I'll warn you that most people around here LIKE their voodoo and won't easily give it up. I suspect this comes at least in part from their Windows upbringing, where it's frequently impossible to understand what's actually going on, and fixing problems often looks a lot like voodoo.
For modern drives (anything in the last 10 years or so) a single pass with zeros is sufficient to make the data unrecoverable without a scanning tunneling electron microscope. In a laboratory that's a seven-digit-plus and months-long undertaking, and isn't going to happen unless you've stolen a nuke or something and some government really REALLY wants to know where it is. If your threat model includes governments at this level, then you must consider physical destruction of the media.
One last note: After you think you've erased a drive, run a data recovery tool on it yourself and see what happens. You may be surprised.