I just don't get why anybody who has successfully built one would ever sell one as they can make far more from keeping it than they ever would from selling it.
By selling to others they would be making their own machines less profitable, as soon as you have one you would soon be able to afford more.
They must have determined that they will make more money in the long run by selling ASICs than by using them.
Possible. However, I think the power savings from ASICs are a good thing for everyone in general.
I love GPU hashing though, and with all the altcoins recently it's still a viable way to go. I imagine scrypt coins will still have high conversion rates to bitcoins and will be valuable, which means GPU miners will have a place.