Look here and here. Google adds a small header into Google Video files so they are unplayable on Windows Media Player forcing you to download their own Google Video Player which is far from a decent video player.
Other instances of Google playing evil? Download a browser and you are most likely to download the Google Toolbar crap with it! Without your permission. Heck, it even came along with the Avast anti virus I installed!
Well, Google what happened to all that talk about open standards, open API, open everything?