Trivial example: a traditional suit-and-tie, senior manager walks by a junior programmer's cube and sees youtube on the monitor and immediately assumes junior is slacking off, abusing company resources. He subsequently spreads negative commentary about junior to his peers.

The problem is both senior's prejudices, AND the fact that he's missing context. Junior might be watching an instructional video. It might be a break after 10 hours straight work. He might be creating videos for the company and uploading them.

In other words, just because you have nothing to hide doesn't mean someone who looks is going to see the whole true picture.