KidSnide
Adventurer
Really the main thing from the perspective of the DM is to try to insure that not ALL party members can fly around extensively all the time. Notice though that most characters don't easily get teleport either, though some do get it for free too. I don't think the 4e designers were stupid. They understood the issue there. It IS easy to get flying, at paragon, if you want it. You missed some items and other tricks too, like figurines, carpets, etc.
I think you're right, in the sense that it is a little easier to break encounters with a fly ability than it is with a teleport ability. So, to a certain extent, the 4e designers made a correct observation that they could introduce a bunch of short-range combat teleportation as an interesting tactical option.
The problem is that "lots of easy short-range teleport" doesn't match my fantasy world. Years of playing with the 1e-3e spell list has taught me that teleport is higher level than fly. I'm not sure that assumption is arbitrary, as I think imitating nature seems "easier magically", but even if it is arbitrary it was a part of D&D for decades.
It's an example of the 4e designers placing the quality of the tactical game over backwards-compatibility in game world. I don't think I can categorically say that backwards-compatibility in game world assumptions is more important than the quality of the tactical game. (Both are important.) But I do think the 4e designers didn't give enough weight to the importance of letting people play 4e in their existing gameworlds without changing quite so many assumptions.
-KS