Increased American activity along the Pakistani border is based more on increased information than increased manpower. Fewer than 2,000 US troops are on the border, and they move mainly by hummer, not helicopter. There are somewhat more Afghan troops and police along the southern and eastern border. There are many more Pakistani police and soldiers on the other side of the border. But over a thousand kilometers of border is used by al Qaeda and Taliban to move back and forth. But much of the border is either too rugged or too out of the way for such crossings. So for the last two years, much time and effort was spent in finding out what the most likely crossings were. There are trails and passes that have been used for centuries, and now they are under surveillance (with UAV and, probably, sensors on the ground), and coalition commandoes (Task Force 121) have been moved in to Afghanistan to go after "valuable targets." More tribesmen have been cooperating, providing information for money (another ancient practice). The Taliban has most tribesmen terrorized into not offering information, but American efforts over the last two years have gradually changed that attitude.
The tradition of corruption and betrayal in Afghanistan is working against al Qaeda and the Taliban. Money talks, and since al Qaeda shifting it's funding from Afghanistan to Iraq late last year, the Islamic radicals have far fewer dollars to play with along the Afghan border.