According to new research from the UK's University of Hertfordshire, two-thirds of memory cards on the second-hand market still contain data belonging to the previous owner, putting their privacy and security at risk.
The university's researchers studied 100 used SD and microSD cards purchased from eBay, second-hand shops, conventional auctions and other sources over a four-month period.
They made a virtual copy of each card, then used regular data recovery software to retrieve the previous owners' files.
The results were alarming, with intimate photos, selfies, GPS data, scans of ID documents and contact lists all there for the taking.
Of the 100 cards analyzed, 36 hadn't been wiped at all before being sold.
Another 29 had been formatted, and two had their data deleted, but it was all easily recoverable.