All a vaguely bright terrorist planning to bomb a building has to do is
Keep moving so as to be well away before someone can complain to the police, even assuming there are police nearby
(As suggested earlier) take pictures of his mates (possibly in silly tourist hats) posing in front of sensitive buildings
Take pictures covertly (presumably not hard to do successfully given the possibilities of checking digital results and then re-trying)
Use video - make film of accomplices walking down street, easy to take brief excursions to include target buildings which you can grab as stills from the video later
Take photographs/video from a moving vehicle
or just the old-fashioned method of using their eyes, possibly making a sketch later if they feel the need.
You'd *think* that someone capable of looking at photographs of buildings and working out how to attack them would probably be capable of doing the assessment about as well by being there, and unless the place was *so* sensitive that a dawdling pedestrian would be suspect to the point of detention, if they perceived much risk of being caught taking photographs, they'd just not take photographs.
Apart from people blowing up car-bombs outside (which surely doesn't take much precise planning of location), or walking in past defective physical security with a bomb to leave somewhere or detonate in a suicide attack, what kinds of building attack are there?
(I suppose the IRA mortar attack springs to mind, but I assume *they* could have just used a map.)
At the very best, curtailing photography just seems to be a significant pain for many regular citizens, which might make things fractionally more inconvenient for a few possible terrorists.