Can I quote some things from pages 28 and 29 in the PHB?
In the paragon tier, your character is a shining
example of heroism, ... You are
able to travel more quickly from place to place, perhaps
on a hippogriff mount or using a spell to grant your
party flight. In combat, you might fly or even teleport
short distances....
In the epic tier, your character’s capabilities are
truly superheroic... ...your whole party might take to the air in
combat.
The game was designed with characters being able to fly at paragon and above levels. I see several level 22 utilities that grant flight (with or without hover) until the end of the encounter. Maybe it's unfair that sorcerers get it at 16th, but it's not completely unexpected. It appears that lack of flight will be the unusual characteristic by mid-epic.
If I were to DM and some of the characters had the power of flight, I'd make sure to account for it in my combats. If the sorcerer, who's somewhat squishy, wants to fly 10 squares up and lob acid bolts all day, then he'll find that he's fighting some other flying thing 10 squares away from where his buddies can help him.
The game's not broken because someone gets flying; It was obviously designed with that in mind. I remember months ago where someone did some stats on the Monster Manual and IIRC at epic a sizable percentage of monsters could fly.
If I'm a 16th level sorcerer and I fly this round, then I'm in the air at the end of the round. At the start of my next round I'm still in the air and as long as I fly at least 2 squares that round I will still be in the air at the end of it. So I'm fine as long as I use this 16th level utility to fly each round. If I'm ever stunned, immobilized, dazed, or something, then things will change. I really don't see the mechanical problem. If for some reason I don't use my fly at-will, I fall. So if I only get one action (dazed?) and I don't use it to fly, then I guess I'd fall and be completing my one other action just before I splatted, perhaps.
Mass Fly Wizard Utility 22
<snip>
Targets: You and each ally in burst
Effect: All targets gain a speed of fly 8 until the end of your
next turn.
Sustain Minor: You can sustain this power until the end of
the encounter or for 5 minutes. If you don’t sustain this
power...
That one's in the PHB. How come no one in here thought that was broken for the last 9 months? How come this 'kiting' problem is only now rearing its ugly head?