Ever since Steve Jobs announced in his Macworld keynote that Apple had sold 4 million iPhones to date and AT&Ts; Rick Lindner said that AT&T had activated about 2 million iPhones, analysts have been trying to figure out where the "missing" iPhones are, according to Eric Savitz at Seeking Alpha on Monday.

On Monday, analyst Toni Sacconaghi offered his latest theory. He’s revised his estimate from unlocked phones from 15 to 20 percent of all units sold to about 27 percent. Apparently, unlocked iPhones are being seen in good numbers in countries where the phone is not officially sold, especially Asia.

Mr. Sacconaghi noted, as Apple is well aware of, unlocked iPhones are a problem for Apple since they receive no carrier payments and it could make it difficult to sign additional carriers.

Mike Abramsky with RBC Capital weighed in on the situation, and came with up with similar data but with a different conclusion. His take was that the unlocked iPhones "are financially positive for Apple," in that they "bode well for global iPhone demand."

Needham’s Charlie Wolf wrote that Apple might have sold more iPhones, perhaps 1.5 million more, over the holidays if they hadn’t introduced the iPod touch.

iPO notes that cannibalism across product lines in the iPod and iPhone families is a topic that analysts always bring up at Apple’s earnings report call in, but Apple has not provided much insight on the topic so far. That’s probably because Apple wants to take action to correct any such issues before investors start to worry about it.