Average was $5,640 per theater on 299 screens, which is virtually tied for second place weekend BO with Scream 4 ($5,656 avg on 3,305 screens). I wouldn't exactly call that "derailing."
"Boosters of Atlas Shrugged: Part I might point to the movie's per theater average to spin it as a success (ex. "it did almost as much per theater as Scream 4!"), but spin is all it is. It's a common ploy to cling to per-theater average to rationalize a soft run. Obviously, it's easier for a small release to have a higher per-theater average than one at over 3,000 theaters (at any rate, Scream 4 was a disappointment itself)."