Earlier this week, reports surfaced that Apple (Nasdaq: AAPL) is working on a built-in SIM card for the iPhone that would allow users to switch carriers at will.

Talk about disruptive. SIM cards, otherwise known as "subscriber identity modules," are pullout plastic pieces encapsulating a chip that contains your records. Make a call, and it's the SIM that identifies you as, well, you to the network.

Carriers use SIMs to activate features, bill customers, and otherwise track your usage. They're also the key to phone portability. Want to switch handsets? Swap the SIM, and the new phone is yours to use.

Domestically, this might not be as large an issue. While AT&T (NYSE: T) depends on SIM cards, differences in Verizon's (NYSE: VZ) and Sprint Nextel's (NYSE: S) networks mean most of their phones don't have SIM cards. Still, GSM users would be free to switch plans and providers. Carriers would be forced to compete even more on price or create contracts so draconian as to discourage anything less than total commitment.

And that, by itself, would create a huge problem. The more commitment carriers require, the more likely they are to force a rebellion that could push millions to Web telephony on open networks. It's this dynamic that has investors salivating at the idea of a Skype IPO.

Would Apple go so far as to create its own iPhone SIM? Sure. We're talking about the world's most vertically integrated tech company, after all. The Mac maker controls (either internally or via tight-fisted outsourcing) the design, component choice, and manufacturing of everything it sells.

Relax, Steve is in control
There's also a very intriguing business reason for Apple to do this: account control.

In tech, account control refers to a componentized product or service delivered by multiple vendors. One assumes control by being the primary invoicer and keeper of customer information. Apple, in controlling the SIM, would keep tabs on users and tell carriers what to charge. You're right if you think telecom executives cringe at the thought of having to bill in this way.

Apple CEO Steve Jobs, on the other hand, must be grinning at the possibility. His company would be the only winner were the iPhone to get its own SIM.

Users certainly wouldn't gain anything. They'd be trading phone choice for carrier choice, buying into a fallacy of freedom disguised as a pitch for openness and wrapped in what's sure to be a brilliant marketing campaign.

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