Here is a clip from the Secrets of Chute Boxe training video by Shogun and Ninja Rua, where they are showing you how to "properly" throw a soccer kick to the head of a downed opponent. Kind of makes me want to actually give it a try some time, lol.

http://www.sherdogvideos.com/store_videos/cb6.wmv

And now here you see said technique applied to competition:
http://www.youtube.com/watch?v=qVOEtWvoxpo


And just for fun, you may also spot the following techniques being employed in that youtube video as well.

Flying Knee
http://www.sherdogvideos.com/store_videos/cb1.wmv

Using Elbows
http://www.sherdogvideos.com/store_videos/cb5.wmv