In my last article on the intelligence coup scored against the al Qaeda network, I pointed out that many of its members could be turned into de facto agents and informants for the United States... without their cooperation or even their knowledge. The U.S. Government's ability simply to track the movements and actions of individuals is incredibly formidable -- assuming its intelligence and law-enforcement organizations know who to track and where to find them.
Obviously, the intel in that 2.7 terabytes of data is probably vast and incredibly significant, giving American forces an overabundance of potential surveillance targets. But the technology already available for tracking "persons of interest" has improved dramatically, as can be seen in this Wired article -- covering technologies from tracking scents to quantum dots.
I should point out that the linked article only covers a handful of potential ways to track an individual. A host of other methods exist, ranging from traditional techniques to other cutting-edge options not normally associated with police or spy work.
Rest assured, the people tracking al Qaeda are familiar with most if not all of these tools, and if they are not using all of them... it is only because too much of the network is folding up (or becoming utterly compromised) too fast.