Here's a good example of how it can really work well: PronunciationBook. The series could not be simpler. It demonstrates the pronunciation of common words, names and brands. It's nothing fancy (and commenters, of course, often beg to differ) but that's why it works, particularly if you're watching it in the Cosmic Panda interface, which makes watching a series seamless and easy.
YouTube rolled out a new interface option called Cosmic Panda about a month ago with relatively little fanfare. I'm a huge fan of the new look. It allows you to scroll through a playlist via thumbnails that slide left to right, and automatically loads the next video in the series. The look is much cleaner, with a dark frame around the video, and clear resizing options at the bottom.
Kasia Cieplak-Mayr von Baldegg is the executive producer for video at The Atlantic.