Big Sister, Big bad, or just a front woman?

[Zvriel Chkies]

Possibley yes.

[Mitchmike]

I think the fact that Big Daddies are always adults is due to hormones. If the Adam was to be taken in by them, it may cancel out with these hormones. Being that the Little Sisters lack the necessary adult hormones, this makes them perfect for harvesting. Now since the Big Sister is in between these two things, it is inevitable that it will greatly effect her (possibly showing a weakness). As seen in the demo, the Big Sister definitely was frantic in her search for Adam. This is probably why she wants the Adam to remain circulating so she is allowed a fair supply of it when it is needed. It seems that indeed she will only be what seems a messenger to a higher power. On each ''errand'' that she takes, she will take in a supply of Adam giving a small portion to that ''higher power'' and keeping some in order to fuel her next run. Thats also probably why the main cause is to kill all the Big Daddies in order to stop the circulation allowing the player to get closer to the Big Sister.

[JimmyTheCannon]

I don't see what Little Sisters having to be kids has to do with Big Daddies having to be adults. The Big Daddies are adults because adults are stronger and larger and make better protectors than children.