Google Docs can help you create an additional level of backup in case your computer explodes in the middle of your presentation. I usually upload an extra copy of my Powerpoint onto Google Docs in case I have any technical difficulties with my computer.
This way, I can use anyone’s computer to access the internet, and play the presentation straight from the cloud. Keep in mind, however, that presentations over 1000MB won’t upload to Google Docs. Also, Google Docs doesn’t support transitions, so this will be a very simplified version of your Powerpoint. I usually like to check it to make sure all the font sizes transferred correctly. Just yesterday I added a presentation that seemed to upload everything correctly, except the font size was just a tiny bit bigger than in was supposed to, and it pushed an entire line of text out of view in one of the slides.
Putting these limitations aside, Google Docs can be your safety-net in case all else fails. If this isn’t enough for you, you can always be paranoid like me, and carry another additional copy of the presentation on a USB drive