I won't get involved in the mechanics debate, but I disagree with this fluff entirely.
The basic concept of a disarm is to force an opponent to retreat or use an inferior weapon - all part of a fun tactical fight. I would have little respect for a DM who allowed a disarm to be an "I win" button, or a player who thinks it should be.
Actually, if you go by the kind of cinematic fight scenes D&D is trying to emulate, Disarm almost invariably falls into one of
either of those categories.
1) If it's a temporary setback for the hero, or villain, it almost never happens more than once per fight.
2) If it's a dramatic "flip the bad guy's sword out of his hand and order him to yield" moment, it always happens at the end of the fight scene--at least until the disarmed character suddenly and heroically springs back into action (you might say "gains a second wind").
Ergo, it seems the happy medium is to have both options:
1) Once per encounter, a character may make a Str vs. Fort
or Dex vs. Ref attack. On a hit, the target is disarmed, its weapon landing in a square of the attacker's choosing up to a number of squares away from the target equal to the attacker's Strength modifier. Situations like Danceofmask's "take the player's weapon away and keep it from him" can be solved remarkably well by the guiding philosophy of 4th Edition DMing:
Don't be a jerk to the players. The same philosophy that tells us "don't put 100-foot pit traps in a 1st-level adventure" tells us "don't hamstring players for the entire fight."
And if players try the keep-away trick on bad guys, so what? Have them carry a backup weapon, and reward the player for a potentially risky tactic (wasting an attack) by putting one monster's attack and damage slightly below where it should be for its level, it's not the end of the world. Elite and solo "legendary swordsmen" types can be kitted out with powers to help them recover their weapons if they're disarmed.
2) In lieu of killing or knocking out an armed target that reaches 0 hp, you can automatically disarm the target as part of the attack that reduced it to 0 hp. The weapon lands in a square of your choosing, up to your Str modifier away. The target is conscious and not dying, but is utterly at your mercy. Until its hit points rise above 0, you may deal a killing blow as an immediate interrupt if it takes any action. This killing blow is a basic attack that automatically hits and automatically kills the target (or knocks it out, if you so desire).