I used to do a lot of work in an electronics lab that had a whole bunch of windows on one wall that looked out onto a hallway. That hallway was more or less the main passage through the building, so it was fairly high traffic. I used to tell people I felt like I was working in the engineer exhibit at the zoo.

i feel uncomfortable when people watch me browsing or worse reading email or the like, but not when coding. especially not when it's colleagues, since it is their project too