Another precision based damage question?

Alright, if you are sneak attacking with a volley against multiple opponents who are all denyed DEX, do you get the sneak attack damage against ALL of them or only the first in the round?

If you were to stab them all with a knife, you would definately get sneak attack damage on every hit, but if you were to fire 2 bolts of flame ala scortching ray, does only the first count?

The lovely post here about the often overlooked Grease spell brought up some interesting points for a wizard/rogue idea I had.

Sneaking

Only the first bolt counts. Check out p. 86 of the Complete Arcane:

"Some weaponlike spells can strike multiple times in the same round. When the caster gets a bonus on damage with such spells (including sneak attack damage), the extra damage applies only to the first attack, whether that attack hits or not.

For example, a 7th level sorcerer/3rd level rogue with Point Blank Shot makes a scorching ray attack at less than 30 feet (two rays)... If the first ray hits, it deals 6d6+1 points of fire dmaage (4d6 normal + 2d6 sneak attack +1 Point Blank Shot), while each subsequent ray deals only 4d6 points of fire damage whether the first ray hits or not."