I read that there's an entire online mode in where you can get some weapons/loot that you can't get in the main story. There was deathmatch an everything, it sounded pretty cool and I knew a bit about that but I didn't knew the focus on online was that big. Though, you can only play with people from Europe.
But how it was for Monster Hunter 3? It seemed to have people for all around the world since I remember seeing a video of someone from Chile playing with a Japanese player.
...or maybe it was Monster Hunter G for Wii? Hmm, can't remember but it was something like that.