The New Yorker magazine has published an excellent piece on this by investigative journalist Seymour Hersh. To give you a feel for the angle and overall tone of the article, it reads in part, "But the Taliban overrunning Islamabad is not the only, or even the greatest, concern. The principal fear is mutiny—that extremists inside the Pakistani military might stage a coup, take control of some nuclear assets, or even divert a warhead.... The former high-level Bush Administration official was just as blunt. 'If a Pakistani general is talking to you about nuclear issues, and his lips are moving, he’s lying,' he said. 'The Pakistanis wouldn’t share their secrets with anybody, and certainly not with a country that, from their point of view, used them like a Dixie cup and then threw them away.'" Like most pieces by Seymour Hersh, it's also peppered with a few revelations of secret dealings and doings that are bound to make the Obama Administration (and the prior Bush Administration) uncomfortable.
You probably already have opinions one way or the other about each of The New Yorker and Seymour Hersh (and they're probably the same). But even if you don't normally like either of these "institutions," you may still want to read the entire article HERE.