Here's an example, about Dell. "How do I know that they don't have a FBI hookup that scans all of the 'bad' drives before refurbishing or disposing, or how do I know that they don't have a contract with the MPAA/RIAA to allow their anti-piracy goons to do that? How do I know it doesn't pass through a group of teenagers who parse it for nudes, as happens at most computer repair shops?"
It's surprising and puzzling that the tech companies don't try to out-do each other to protect their customers' data. True, most users aren't thinking about it now, just as most people weren't thinking about oil spills before the calamity in the Gulf of Mexico. I don't doubt that in the future, snooping by people and companies is going to be a huge problem, a competitive one, as malware is today.