The U.S. Air Force fears that the Taliban may attempt a terror attack against the U.S. bases (in Nevada and Arizona), where the operators control (via satellite link) Predator and Reaper UAVs flying over Pakistan. These UAVs have killed dozens of Taliban and al Qaeda leaders in the past year. The terrorists have fired mortars at the Pakistani Air Force bases that the UAVs operate from, but these attacks have been too limited to do much damage, much less interfere with flight operations. The Taliban are getting desperate.
It's unlikely that the Taliban could carry out an attack on the well-guarded bases, in the United States, containing the UAV operators. But the terrorist chatter (electronic, and on the ground) is getting increasingly nasty and strident.
Dozens of civilians in Taliban controlled tribal territory have been accused of being spies (providing location data for the UAV attacks), and executed. Most of these victims are believed to be innocent, as the Taliban have been unable to produce any concrete evidence that the U.S. is relying that heavily, on informants, to provide target locations. Meanwhile, no matter what the Taliban and al Qaeda do, the Hellfire missiles continue to find their targets. Thus carrying out an attack on the UAV operators, in the United States, has become a popular subject of conversation. At least enough for air force security officials to take notice.