I found it very intriguing to see a document reader used to project an image from a smartphone the other day. The computer wouldn't work for some reason, but other technologies were used to provide much the same effect. Would the lesson have fallen apart without the visual on the screen, I don't think so, but it did help provide a bit more perspective.
Watching this scenario unfold, I realized how important it is to have a "back-up plan." I don't think it's realistic to rely solely on technology. If your technology won't work, and your whole lesson or presentation was to rely on that, what do you do? Can you fill a whole class by lecturing or creating improvised group activities when you can't remember the exact details of your presentation? One would hope that a presenter would be knowledgeable enough about what they're presenting that this wouldn't be too much of a problem. However what if you're filling in for someone? Or maybe you were asked to present on a topic at the last minute, and it's something you're not very familiar with. I'm someone that usually prefers to have a piece of paper that I can quickly glance at for a reminder, so hopefully I'll never run into this problem. I will definitely always be sure to check the technology I'm hoping to rely on before class starts though!
In my last practicum, I ended up doing a musical theatre number with the drama class. We took the song Taking Care of Business, and rewrote the lyrics to make it about our class. I downloaded a karaoke version of the song and put it onto my iPod. We had a fantastic theatre in which to work, but neither my CT nor I had any idea how to use the sound system. I frantically went in search of the dance teacher, who I knew was quite familiar with the machine. Fortunately she was able to come and show me how to work it before the class started. I think I would have been quite embarrassed had I not sorted everything out before the students arrived though!