Bukkit/CraftBukkit — comment on commit 5db278fce7466bb417aa6180775bb4a5464756d6
File:  line 0
By jrtc27:

Maybe not any more - Minecraft Snapshot 12w07a's change log includes:
* Multi-player light calculations do no longer cause affected blocks to be transmitted to the clients, instead the clients will recalculate the light on their own