I have been watching videos about Minecraft (I haven't bought the game yet. I'm still waiting for the full version.) and I realised that you can't sell or trade or buy or anything like that. I can understand that the game is about surviving and mining and trying to live of the resources you find, but many people want to take Minecraft to the next level and start building dream homes and skyscrappers and gigantic buildings. I think trade and shops and all that stuff would be good for those who want to live like Minecraft kings! You could even make a server especially for it so that if you don't want trade or money in the game, you can go to a server that suits you. This is my opinion and I think that this would make the game more fun to some people. Also, some people are scared to go out and fight zombies and giant spiders (I know I am!) so trade and selling would be a big hit so that you could still get resources without nearly killing yourself!
Go google "colony mode".