Images and Text Do Not Mix
This PowerPoint presentation on cars (we know it's about cars because an introductory slide consists of the word "CARS" in huge, garish orange-and-blue letters) puts all of its images in the background (after applying a little tasteful fading), with paragraphs of text overlaid on them. This accomplishes the difficult feat of making the images hard to look at and the text hard to read. Perfect--a lose-lose situation!
The presenter could have consolidated the text in one part of the image, using the image's horizontal guiding lines; but that didn't happen, so the slide manages to look sloppy as well as unreadable. Bonus points for misspelling "carburetor."