In the heat of the presentation design process, you can easily forget some basic image house keeping. You search Flickr for a Creative Commons image, find it, CMD-C/CMD-V into PowerPoint, go back to find the name of photographer and put it in small letters on the PowerPoint slide. Done. What next? PowerPoint reduces the resolution of the image to 72 DPI, and crops off the bits you do not use (if you compress files). Also, inside a PowerPoint file, it is much harder to find that image when you want to use it later. So instead: save your file to disk with a good description, including the name of the photographer. If you want, you can add meta data in workflow applications such as Aperture. In this way, you are building on a useful photo library for the future.