O2 is likely to become Apple's biggest cheerleader. The mobile operator, which is the exclusive iPhone carrier in the UK, said that the iPhone quickly became its "fastest-selling" UK handset ever, according to iLounge. "The UK added 483,000 net customers in the quarter including 276,000 on contract, the highest number ever, helped by sales of the iPhone," Matthew Key, CEO of O2 parent Telefonica Europe said when announcing the company's fourth-quarter results.

Earlier this week, O2 said that it has snagged exclusive rights to sell the iPhone in Ireland as well, which it will begin doing on March 14.