Garfield is probably the likeliest of these. I'm just unsure of his chances as he does not have a ton to do in The Social Network. The film fails to shift any kind of real focus over to him. He's quite good but none of the supporting performances have the gravity they need. I'm perhaps unwisely predicting John Hawkes on the basis that he is amazing, everyone's worked with him, and the film is going to be seen.
It wouldn't be unwise, but it could be unlikely unless Winter's Bone scores a Best Picture nomination.
Original Score? The film has the best composition of the year but on the whole the Academy tends to nominate the same people year after year. I'm predicting Alexandre Desplat, A.R. Rahman, Hans Zimmer, James Newton Howard for The Tourist, and someone else.
Or they have a tendency to nominate someone new based on the Best Picture pedigree, like Buck Sanders, Jan A.P. Kazmarek, Gustavo Santololallo, Howard Shore, James Horner, Danny Elfman and...wait for it...A.R. Rahman. How else do these composers who get ad nauseum amounts of nominations begin?
Cinematography? The film looks amazing, but it's not a pretty film, it's a gritty film. It's a film of interiors in a category that time and time again honors exteriors.
Gritty has worked to the advantage of numerous films: Saving Private Ryan, The Diving Bell and the Butterfly, The Hurt Locker, Slumdog Millionaire, Children of Men and Good Night and Good Luck. Generally, it's if they combine the gritty camera work with a finesse of beauty, which the Social Network not only achieves, but also has that technical aspect of being completely shot digitally, which the last two films that have won were completely shot on digital cameras.
Sound Mixing could certainly happen. There's no reason why it couldn't except I think there are more viable contenders for the prize like Black Swan, Inception, Shutter Island, Toy Story 3, and True Grit.
Here is where I completely agree with you. While when I watched Black Swan, I said to myself "what a great, subtle psychological use of sound" with the feathers rustling in the background or the pulsating volumes to convey Nina's state of mind. However, I didn't get that sense watching (listening) to The Social Network. I didn't go "wow, listen to how crisp that dialog was" because, honestly, it sounded like every other nicely recorded dialog heavy film. So, Sabin, while I wouldn't be surprised if The Social Network was nominated for Best Sound Mixing, I'm not really expecting it.
The Social Network doesn't need a ton of nominations to win.
True, while it won't come close to the number of nominations that The King's Speech or Inception are most likely going to get, it will, at this stage in the game, most likely win.