Net Widening

The NY Times reports today that government officials seek heightened access to personal passenger information held by airlines and the global travel reservation services that handle bookings for most major airlines. Currently they enjoy access to the info contained on your passport as well as to your itinerary, but only fettered access (they can sometimes get it--but they're very limited with what they can do with it--i.e. which law enforcement agencies they can pass it on to) to your credit card information, rental car and hotel plans--even what size bed you've requested at the hotel (I hear terrorists prefer two doubles, non-smoking and extra shampoo). Civil libertarians, of course, are crying foul, and it remains unclear whether these changes will be instituted. For now, homeland security officials want such information only for international travelers, but it's only a matter of time before the policy extends to domestic passengers. Before signing on to such changes, or dismissing them reflexively, I would want to see evidence for their efficacy. What precisely is the rationale?