See also:

http://news.ycombinator.com/item?id=1740482

http://news.ycombinator.com/item?id=1738560 <- This one has the comments

http://news.ycombinator.com/item?id=1738013

http://news.ycombinator.com/item?id=1736805

http://news.ycombinator.com/item?id=1736694

I seriously can't even begin to describe how awesome this is. Minecraft is what second life should've been, a complete virtual environment where people can manipulate things however they like.