Letting a company like Best Buy fiddle with your computer in the hopes of fixing a defect or perform a repair is already a huge exercise in trust.
The problem with all of this is of course that there’s no way to just see illegal material when snooping through a customer’s computer. Without probable cause it is illegal to search a device in the hopes of determining whether or not the owner is a criminal, and absolutely outside the bounds of what someone would reasonably expect a Best Buy employee to be doing.
Just another example of our Constitutional rights meaning nothing to the FBI.