Private Servers, but with a catch
Like TF2, private servers could be used to explore the world, and build with out problems. It would allow us to play around with our creations and friends without strangers getting in the way. If a server had to much data on it, we could make a private one, with downloadable backups so we could share our creations online. Think of how much more popular this would become.
If you read that all, I'm impressed. I'd be much more impressed if you did this suggestion.
build in ur pocket universe, only you can go there (use the purple telepad at /root)