With modern wear-levelling algorithms, is there any way of actually guaranteeing that data is gone off of flash memory anyway, short of actually physically destroying the chips themselves?
I guess one way would be write junk data to it for x
passes... with x
being a fairly large number (probably higher than a Gutmann wipe, which is 35 passes). Then leave it absolutely full to the brim with said junk data.
That said, a quick search came up with this program
for Android which supposedly secure-erases data.
To be honest, all that reddit post does is highlight how lacking in awareness most people are when it comes to their privacy and personal information.
A lot of it is out of your hands regardless - there is nothing an individual can do to, say, stop their government losing personal information about them (see: UK Govt losing child benefits database, military records, etc etc...) because when it comes to wanting data on you, the Govt isn't going to take no for an answer.
Nor is there really anything you can do against a company losing your information (see: Sony hack, TJMaxx hack, Lush Cosmetics hack, and so on...) except don't use them, or if you have to use them, only use cash. This, obviously, means you can only use high-street stores, as mail-order, phone-order or e-tail stores will need name, address, credit/debit card info...