Why Do Movies Get Snubbed?

One thing from Nate Silver's Oscar liveblog really stuck with me. At 8:28 he wrote this: "Discuss: the reason why Dark Knight and WALL-E weren't nominated for Best Picture is because everyone who was going to see them has already seen them anyway." While I wasn't able to confirm his theory, I did run across some interesting stats over at Box Office Mojo. This year the nominated films made an additional $104.4 million after nomination (or 35.6% of their total take). That is the second highest percent gain (only behind 1988's 38.2%). The Reader pulled in 64.2% of it's total revenue post nomination while Slumdog pulled 53.9% (and sure to grab more).