[notacoward]

The big problem with erasing SSDs is that when you think you're overwriting something you're actually writing new blocks (because of the translation layer). How many iterations do you have to do before you're certain to have actually hit every physical block? Nobody knows. Maybe infinite. Non-zero data blocks might not be readable through the flash drive's front-end interface, but they're still sitting there on the actual NAND chips. That's why secure erase was added (and even that seems to be less than fully trustworthy).

[m4rtink]

One iteration of grinding the drive to fine powder/melting it down should be enough. Anything else might be insufficient.

[gowld]

That's a good way to erase a disk, but horrendously expensive if all you want to erase is a single file.