This is a really interesting article by Dan Visel. However, for the article to really work you need to see his illustrations, so go on over and take a look:
There have been a raft of reviews of the new Kindle and the various iPhone reading applications lately. In general, reviewers are more positive about the experience of reading from a screen than they have been in the past. However, I’ve noticed that one enormous factor in reading tends to get passed by; maybe it’s not something that people notice if they don’t think about book design. See if you can identify it from these screenshots, which you can click to enlarge.
Why don’t these reading devices hyphenate their lines if they fully justify them? This isn’t, for what it’s worth, a problem that affects more than just these devices; plenty of text on the web is fully justified and has no hyphenation. The problem is that hyphenation is trickier than it might initially appear. To properly hyphenate a paragraph, the hyphenator needs to understand at least something about how the language that the paragraph of text is written in works.