When using a power like Bolt with the Additional Bolts option, does any '1' on any of the Spellcasting rolls invoke a Backlash for a character with Arcane Background (Magic). That is if you roll three 1s casting three additional bolts do you get three Backlashes?
When casting additional bolts, you roll as you do with automatic fire. This means for three bolts you roll 3 shooting die and one wild die. This means that it is very possible that you can wound yourself with backlash as it is possible to get multiple 1's.
Oh, and to clarify - you don't get the -2 penalty for automatic fire when you cast multiple bolts.
See the following links for an official take:
A close reading of the rules in the Explorer's Edition implies that there is only one roll needed to cast the spell, regardless of the number of targets. See page 85 ("Range"):
The arcane character’s skill roll acts as both his “casting” and attack total for these type of powers (Weird Scientists use Fighting or Shooting as usual instead).
There's no mention of requiring additional spellcasting rolls for targetting either in the sections on how Powers work or in the text of Bolt. This agrees with my sense of the purpose of the power when used by an Arcane background – emulating D&D's magic missile – with all the bolts being targetted by the success of the casting rather than having to be individually guided.
In this reading of the rules, you only have one roll for one chance of backlash. If a GM's interpretation or house rules requires additional rolls for targetting purposes, I'd strongly advise them to consider making these extra to-hit Spellcasting rolls not use the backlash rules. Otherwise, additional bolts is just not worth thinking about.