The speed of light has not improved since the days of Quake 3. Network gaming code must still be tolerant of latency up to 100 ms or more. At best, network connections today are a lot better than back then but at worst, they are as bad as they used to.

Quake 3 has also got pretty sophisticated client side prediction code to make things seem instantaneous to the players. This is much more complicated to do in Minecraft where the whole terrain may change and lots of race conditions may arise.

Network game code may seem like a solved problem but it's still a complex distributed soft real time software system where solutions are highly application specific. What works for Quake isn't necessarily good for Command and Conquer or Minecraft.

The big difference is that the map in Minecraft is constantly changing which can in turn change players position and potential actions - Quake 3 was comparitively much simpler, more or less just a coordinate and velocity vector.

But I agree, there is no reason for Minecraft performance to be so bad when there are only 2 people on a server just mining one brick at a time!

> The big difference is that the map in Minecraft is constantly changing

Not quite. The map in Minecraft changes. But if you optimize the game for the "constantly changing" case, when it usually changes less than 1 block per user per 10 seconds (and even that is high), then you're going to end up with code that doesn't handle normal behavior very well.