This is the sort of thing I'm interested in. I guess it doesn't affect gameplay much, but it seems very unusual. Take the Eastern Plaguelands, for example. When you first walk in, there's a cart. If a friend and I (ungrouped) walk up to that cart, and I take the cart, do I disappear? Probably, from what I'm reading. And then I make it to the first tower, and I appear again, but he can't see the cart. Maybe there's some other object in his phase where the cart is in mine, so that he can't just walk through it...

And what about Andorhal? That whole middle town is a big phased place. If I'm at a different phase from someone else, that would be like a black hole to them. I walk up to the town, and disappear. I take a step back, and there I am! Is that really how it works? Having this sort of thing all over the place seems like it would kill the social aspect of an MMO. It moves things in the Guild Wars direction, where everything but a few central hubs are completely instanced. Obviously it's not to that degree yet, but implementing phasing in all the major quest lines means you're more and more unlikely to interact with players out and about in the world. Isn't that what MMOs are all about?