I'd have to say that's not quite true @Gorzoid. Take the OC mod out of it and say you and I are in a server game. I am looking at a block on my screen and decide to break it. I click the mouse button, my copy of MC initiates a request to the server, server takes that, changes it's database to reflect the change (if the change is valid), and then my copy of MC gets info back. All a simplified look at it MC. On that same track, you need info about how I impacted our shared world, so you also see it as the server reports to your copy of MC that the block is broken.
The same could be said of