I like building with others, but usually it just doesnt work.
1) Freebuild: I've yet to see a good one. Usually people start spawning weapons and fight each other. If they build, you can bet that one person builds a medieval castle next to someone else's spaceship. Also: I'm sorry to say, but 80% of all blocklanders I've met are bad builders and/or too lazy to build something decent. And my expectations really aren't that high.
2) Freebuild with a theme (community build): can sometimes work, but only when heavily moderated. For example, if you have a medieval themed freebuild, you can bet there will be at least 5 different castles in it, but not a single windmill or bakery in the village (if there even is one). And you still have the problem that most people can't build, so you'll have to delete their builds (which will cause them to whine and leave) or learn to live with the ugly builds...
3) Themed build with friends: (preferably on a passworded/LAN server) This is the proper way to get it done. You need friends, however...