New attacks on oil industry workers in Saudi Arabia confirm that al Qaeda has shifted its focus, via an indirect means, to a new American weakness: oil. These attacks keep the ~$8 per barrel terror premium on oil in place (effectively, a ~$600 m a day "terrorist tax" on the world), however, due to diminishing returns from these tactics, the premium will not increase much from these attacks. There are still some potential long-term returns that can be gained through the departure of foreign workers (particularly oil industry workers and their families) from Saudi Arabia. If these departures occur (Saudi Arabia relies on 6 m expatriot workers, many of them in the oil industry), they will impact the ability of Saudi Arabia to build additional capacity (which will be difficult to do under even ideal conditions) necessary to off-set rapidly rising demand from China (which according to current demand trend lines will suck up all global reserve production capacity in less than two years).
I think it is extremely likely that we will see a continuation of these attacks on personnel, however, the most gratifying feedback loop (for terrorists) is the price of oil. This price will not increase dramatically (with $50 as a target price -- which Stephen Roach indicates will result in a global recession) unless attacks shift to (primarily Saudi, although this isn't the only potential venue for attacks) oil infrastructure. As a result, expect al Qaeda to shift, soon.
To adapt successfully, the western states need to adopt market indicators as a measure of security success. A failure to do this will result in a misallocation of security resources.