So this, from Inside Mac Games, makes me once again want to start back up my char...
Nethaera: Why are we allowing players to dual spec after all this time?
Ghostcrawler: We really felt like this was a great way to increase the flexibility available to players and encourage them to take part in more aspects of the game. To use just one example, some players like to participate in both raids and Arenas, which is awesome behavior that we want to promote. But, there are some talents which are more useful in one part of the game than another.
That and some texts from an old guildie, that is. Man, I wish real life wasn't so time consuming. *sigh*