Maybe you can blame this one on the titles. Considering the literacy rates in America (just mention subtitles to a prospective audience member and watch them run screaming into the night), titling a film Sanctum is definitely a risk, especially when you consider that you've just saddled a film featuring cave divers with a name that sounds uncomfortably close to Rectum (no doubt the name of the XXX parody already being written in Larry Flynt's deviant little mind). Perhaps he had gained some confidence regarding the title after the success of Inception, not fully grasping how long American film audiences would put up with theater marquees resembling SAT questions. So when it came to picking a film to watch this weekend, most moviegoers no doubt decided to forgo the time it would take to look up the definition of "Sanctum" (noun: 1. a sacred or holy place, 2. an inviolably private place or retreat) and just opted for the blatantly obvious and descriptively titled film. Then again, maybe they're just fed up with all of this 3D crap.
Behind that little chocolate coated goodness, there are no real surprises this weekend. A number of the top ten films are Oscar nominees, as is to be expected, although Ashton Kutcher still holds the title of King of the January Release with No Strings Attached at #3. The King's Speech rides it's Oscar Nominations with pride at #4, and the thankfully Kevin Smith unrelated Green Hornet flounders in mediocrity at #5, looking very unlikely to earn its Hardee's-sponsored money back.
On a side note, I think it is worth pointing out that out of the top twelve films this weekend, only one of them boasts a budget of over $100 million (with no hope of earning its money back), and nine of them at under $50 million, with the three costing under $20 million already grossing more than the budget of the disappointing Tron: Legacy. So much for 3D. Suck it, Cameron.