If you think about it, the front-runners in 3 of the 4 acting categories are all villians, or very, very shady:
Best Actor: Daniel Day Lewis in There Will Be Blood and Johnny Depp in Sweeney Todd.
Supporting Actor: Javier Bardem in No Country For Old Men.
Supporting Actress: Amy Ryan in Gone Baby Gone.
With the exception of Bardem's character--who seemingly has no redeeming characteristic save for an acutely ironic sense of humor--the others, at least, have some redeeming qualities (I'm assuming about Day Lewis in There Will Be Blood).
"...it is the weak who are cruel, and...gentleness is only to be expected from the strong." - Leo Reston
"Cruelty might be very human, and it might be cultural, but it's not acceptable." - Jodie Foster