Interesting backgrounder on Abbottabad. From the article:

So Abbottabad emerges as something of a way station for al Qaeda and associated groups. Geographically, that makes sense. As the crow flies, the city is just over 100 miles from the border with Kunar province in Afghanistan, an area where al Qaeda has kept a foothold since 9/11. Even with poor roads and mountainous terrain in between, the journey can be completed in a day. It is even closer to the restive tribal territories.
In the past two years, the Pakistani army in this area has been preoccupied with reversing the gains of the Pakistani Taliban, rather than chasing down the remnants of al Qaeda or launching the offensive against militants in North Waziristan that Washington has long demanded.
The area to the north of Abbottabad saw a surge in Taliban activity two years ago, as the Taliban sought to extend their influence from the tribal areas that border Afghanistan into what was North West Frontier Province, now called Khyber Pakhtunkhwa. The town of Buner, just 30 miles from Abbottabad and 60 miles from Islamabad, fell to the Taliban early in 2009. They also established a training camp close to the town of Mansehr, a few miles from Abbottabad.