Allies?

[Epinephrine]

So, how does one determine who counts as an "ally" for the purpose of things like a Marshal aura, a Bard's song, or a Dragon Shaman's draconic auras?

Does it depend on the effect? On perception, or intent?
If your ally is dominated, does he cease being an "ally"?
If doppelgangers looking just like your party attack, and you can't tell the difference, do the doppelgangers benefit? Or does nobody?

Is it a decision the buffer makes (in the case of a Marshal, choosing to call out advice?) or is it intrinsic to the intent of the "ally" - if they intend to serve as your ally they mystically benefit from a draconic aura?

How do you rule this type of thing?

[Chronos]

It's whoever the source of the effect regards as an ally, so yes, it basically comes down to the marshal's or bard's choice as to whom to affect. Of course, usually the choice is pretty predictable: "I consider as allies myself, and Bob's character, and Joe's character, and Joe's character's familiar, and Frank's character, and Frank's character's cohort, just like in the last fifteen battles".

[KillianHawkeye]

Depending on the system, it is sometimes questionable if you are your own ally. I think in 3.x you were your own ally, but in 4E you are not.

[Epinephrine]

It's whoever the source of the effect regards as an ally, so yes, it basically comes down to the marshal's or bard's choice as to whom to affect.

So, in the case of doppelgangers, since the ally doesn't know who to grant the bonus to, they decide to grant a bonus to both, neither, or pick one at random?

Do bonuses automatically kick in, or is it a free action to select a new target (for example, an elf step out of the bushes, hacking into your opponent's exposed back. Does he get your bardic music bonus, since you want him to, or do you have to wait until your turn to grant him the bonus as a free action?)

If the party is currently benefitting from an aura (like a dragon shaman's Energy Resistance), but the lights go out, and when they come back on there are two copies of everyone, does the party still have resistance? Can you safely let loose with a breath weapon, knowing that it'll burn the enemy, but leave your team untouched? Or since you can't tell who your allies are, are you faced with the choice of who to protect?

[RebelRogue]

The user of the power chooses what is and isn't an ally. However, you can never be forced to be an ally, so you may always deny the effect of any such power if you wish.