One of the claims that the mobile industry likes to perpetuate is that SIM cards (and subscriptions) are "personal" and therefore position cellular operators as ideal providers of identity management services.
I've long thought that there were lots of assumptions about the one phone = one SIM = one person view of the world that were extremely fragile. Most obviously, it's very common for one person to have multiple SIMs, but that's not a particularly critical issue in most cases. Having multiple "identities per person" is pretty valuable to most users, anyway.
More interesting is the opposite problem - multiple people per "identity". This has long been the case in fixed PSTN and broadband, where the basic subscription unit is a "household" not a person from the operator's view - perhaps with the "bill payer" identified as a named individual. The rest of the household members are generally anonymous, despite years of attempting to offer various family services to help distinguish the bill payer from their spouse or children or flatmates.
The same thing is happening in mobile. There have been fixed cellular routers for some time, albeit achieving limited popularity. But two new developments have the potential to create a massmarket disconnect between SIM and individual:
- MiFi-type devices, as sold by companies like Novatel and Huawei, which act as "mobile hotspots" for multiple users connecting via WiFi, without any form of personal identification. In theory there are mechanisms for tracking back individuals via WiFi MAC address, but in reality that's very complicated, especially for shared devices like PCs.
- the new WiFi Direct specifications from the WiFi Alliance, which essentially make peer-to-peer WiFi easier to use and more like Bluetooth-on-steroids. This will enable adhoc connections between devices, and I'll bet one of the most popular will be some form of bandwidth-sharing or load-balancing between multiple phones or other products. I can think of numerous "reasonable" use cases here, eg de facto user-driven "national roaming" to work around coverage blackspots. I'm sure there will be some cool connection-sharing iPhone or Android apps, as well as ones for PCs. Yes, there will be a ton of security issues, but I bet some could be solved via social-network reputation techniques (eg "share my connection only with my Facebook friends, and friends-of-friends")
If you have 10 random people in a room collectively & collaboratively sharing 5 bridged WiFi-to-cellular accesses, you can pretty much forget about an notion of individual identity being traceable through the SIM. Add in anonymous prepay and it's even trickier.