Several things come to mind:

• by giving your password to someone, you are essentially consenting to them accessing your data
• your data should be backed up before you bring a device in so it can be wiped off if they need to access the OS
• certified technologists exist and they have to adhere to a code of conduct
• best buy and the ilk do not hire technologists… you get what you pay for
• if a technician is paid to back up your data, then they need access to your data, if they find porn and if it’s bad, they will report you