Yesterday I introduced Google Docs to my students. In my first hour class, I was projecting the Google Docs screen onto the screen in my room, walked over, and tapped the screen to switch the view. Nothing happened. Puzzled, I went to tap it again, then remembered that I wasn't using my Smart Board, I was using a regular overhead screen. Woops, no wonder it didn't work. None of the students noticed, so I got to keep full cool nerd points for block 1.
Needless to say, I switched back to the Smart Board for the rest of the day. :-)