Just posted in EQ Vault - it was posted by Brad McQuaid (EQ's producer and Lead Designer) on the official forum. I think it makes it clear his philosophy and why talk of expanding binding including new high level songs is a waste of time. (To make MYSELF clear - HIS opinion - not mine)...

Binding is set up the way it is and always has been for balance. It is part of the death penalty and is there to pace the game.
The idea is that casters are more prone to dying and thus can bind in more places. It still paces the game, however, because groups need to wait for melee characters to return. If melee characters could bind anywhere it would alter the pace of the game, further minimize the death penalty, and let well balanced efficient groups just scream through dungeons.

I realize some players reading this might think that sounds great, but there has to be a pace to the game and a penalty for dying.

We are also considering making it such that casters cannot bind in Expansion dungeons (the fact that they can now is actually a bug that is too late to fix for the rest of the world).

-Brad