Apple's iPhone has rarely been out of the spotlight since it was announced at Macworld Expo just over a year ago, but this time analysts and tech enthusiasts are not deliberating over new features, price cuts or the potential for an iPhone 2 launch during 2008.

It's the mystery of the missing 1.3m iPhones that's causing a stir, with huge discrepancies in Apple's reported sales figures and those of its partners. Steve Jobs' firm claims more than 3.7 million iPhones were sold last year – 1.3 million more than the estimated 2.4 million shipped by the company's network partners. So how does Apple account for the missing handsets?

Macworld UK has two suggestions – firstly, that a significant number of iPhones bought over the holiday period at the end of 2007 weren't activated until after the new year (and so didn't make it into Apple's 2007 sales figures). Alternatively, a huge number of iPhones are being snapped up by people who are determined to unlock the device so it'll work on other mobile networks.

Apple has insisted it will do everything in its power to ensure people can only use the iPhone with its official network partner in each country, but the figures suggest one in three iPhone buyers are sidestepping the likes of AT&T in the US and O2 in the UK.

That seems like a high figure, but we're looking for feedback on your experiences with the iPhone. Do you have an unlocked handset, or have you seen one working in the wild? There are plenty out there, and the process for unlocking an iPhone is freely available in various online forums. But is the practice really as widespread as the figures suggest?

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