Before patch 4.0.1, this talent was sometimes known as the "Hunter I.W.I.N. Button" — this is because it would make you immune to all types of crowd control for 10 seconds, and most classes rely on crowd control to win a fight to keep you in melee range during combat.
Trivia
The talent description before patch 4.0.1 would appear to be a reference to the movie The Terminator which contains the line, “It can’t be bargained with, it doesn’t feel pity or remorse or fear and it absolutely will not stop ever until you are dead”.
Patches and hotfixes
Hotfix (2016-08-26):The Beast Within (Beast Mastery) now reduces the cooldown of Bestial Wrath by 15 seconds (was 30 seconds).
Patch 7.0.3 (2016-07-19): Re-added as an honor talent and redesigned. Reduces the cooldown of [Bestial Wrath] by 30 sec, and causes the hunter to become immune to all Fear and Horror effects while Bestial Wrath is active.
Patch 4.0.1 (2010-10-12): No longer increases damage by 10% or gives the hunter immunity to crowd control for the duration.
Patch 3.2.2 (2009-09-22): The duration of this talent has been reduced to 10 seconds. In addition, hunters with this talent will do 10% additional damage at all times.
[Bestial Wrath]
Hotfix (2016-08-26): The Beast Within (Beast Mastery) now reduces the cooldown of Bestial Wrath by 15 seconds (was 30 seconds). 
