An interesting part of the poor, murdered Imran Farooq of the MQM (in London, no less) is the story of how he was in hiding in Karachi from 1992 till 1999. Seriously. If you don't know, this was a man who went into hiding when Pakistan's military, intelligence and the Sindh police were searching for, capturing and killing key members of MQM. If this guy could stay in hiding in Karachi, with a sufficiently dedicated network, one could go into hiding in Pakistan, and the authorities and establishment would be incompetent and incapable of penetrating your support "netowrk" to find where you are. And mind you, this "hiding" was in Karachi, the largest city in Pakistan.
So what this means, is that if you want to go into hiding in, let's say, Khyber Pakhtunkhwa, or not ecen Khyber Pakhtunkhwa but the under developed Federally Administered Tribal Areas, and you want to make sure that you aren't caught, it may be a trick that you could eventually pull off.
Just ask Ayman Al Zawahiri.
Or Hakimullah Mehsud.
Or Qari Hussain Ahmed.
Maybe ask Maulvi Faqir Mohammad or Mullah Omar Khalid?
What's that you say, you can't find them? Maybe that's because a guy showed, in the most populated city of Pakistan, that you can hide out in ANY part of the country if you have a dedicated (or fanatical) enough support network.