For the last five years Pakistan has tried, without success, to block the use of anonymous cell phones. Recently the government had to back off on threats to block calls made by someone who bought a SIM (Subscriber Identity Module) for their cell phone using fake ID. The government has not been able to come up with a foolproof system that will prevent criminals and terrorists from buying SIM cards that cannot be traced back to the purchaser.
Two years ago Pakistan shut down cell phones owned by anonymous users. This turned out to be a huge number, eleven percent of 88 million SIM cards in use at the time. That caused such a public uproar that the government had to back off. The year before that this effort was stymied because, in the tribal territories, dealers were not obeying new rules that required them to get positive ID from cell phones buyers. Four years ago the government blocked the use of 10.5 million unregistered (anonymous) SIM cards for cell phones. But the bad guys figured out how to get around that.
These SIM cards are the type favored by gangsters and terrorists. In most parts of the world you can move your cell phone service from one phone to another by simply removing the small (25x14mm) SIM "card" from one phone and inserting it in another. SIM cards can also be bought just for the minutes stored on them. Police have long noted that terrorist bombs are often set off using a cell phone with an anonymous SIM card. It's not uncommon to raid a terrorist hideout and find hundreds of anonymous SIM cards.
Four years ago there was already a thriving Pakistani black market in SIM cards that were registered with phony information. The Taliban and drug gangs knew of their vulnerability and could not run their operations without these communications tools. Gangsters in other parts of the world have developed ways to lessen SIM card vulnerability and the terrorists are learning as fast as they can. In the meantime, it's getting them killed or captured when they use easily identifiable SIM cards.
It was believed that, with anonymous cards more difficult to get, it would be easier to track down bombs that use cell phones for detonation. But Pakistan is a very corrupt place and merchants were able to circumvent the new regulations by simply bribing any police who came by to check SIM card registration. The cell phone companies also resist these government crackdowns, as it is bad for business.