Prior to Cataclysm this was the only true ranged area damage the Hunter can do. Since Cataclysm pre-patch Multi-Shot takes the role of ranged area damage.
Limitations
This is a channeled ability, so any damage taken will cancel the effect. (As of patch 2.0 this can be overcome with rank 3 Improved Barrage talent.) Also mobs may leave the area of effect.