How do you hang a computer on the wall? Be careful and there isn't much that can go wrong.
Why do you hang a computer on the wall? Well, my friends think that it is for:

Letting the components run cooler

Making it easier to swap things out

Helping them with their investment in the stock in that company that makes cans of air for cleaning the dust off stuff

The actual reason was that I saw one on the 'net and thought it was cool and decided I wanted a wall-mount of my own.
One day I'd like to get some real wood and make a very attractive wall-mount, but for now, I'm really happy with how it came out. It does run cooler -- my Athlon XP1700+ is overclocked to 1800+ and runs below 40 degrees under full load. I don't foresee putting it back in a case in the near future.