Deciding that because you simply must have your site in a particular font with the text wrapped in exactly a certain place, you create all of your pages as graphics of text. These people also neglect the alt tags and title tags and use file names like "page1.html" The end result is a site with not one word on it.

I have seen at least five sites done in this way, and guess what? You can't find them with a search engine no matter how hard you try.