Eyebrows -- those highly mobile facial features that always get raised when people are astonished -- got a good workout Tuesday at Apple's quarterly earnings call. Apple COO Tim Cook surprised analysts by stating that some customers are spending their money on iPads instead of new Macs. There's long been suspicion that the iPad has been eating into sales of laptop and desktop PCs. But this may be the first time Apple's acknowledged that its tablet may also be eating into its own computer line.