Well, in answer to both slobodan and Russ, the fact is that I am just suggesting the other side of the debate have a fair hearing too, which in a community of photographers, whilst a difficult thing to expect, is none the less reasonable for it.
There is no harm in the simple snap, per se, it is the fact that the simple snap isn't, perhaps, always that innocent. Concerning the notices about bridges, airports, stations and so on - of course there isn't any harm shooting those things as beautiful, evocative photographs; but there is something dangerous about too much structural detail being studied, the understanding that can be gained from that regarding construction, areas of weakness and vulnerability, there's no end to the dangers that can be pulled into the argument, but as with much, it is the intent that is the difference between the benign and the malevolent. I guess the fuzz has little choice but to try and err on the side of caution, particularly when they are the same people who are ever blamed for lack of foresight when things do go wrong; a no-win position for them, then?
How are photographers endangering national security, was asked: well that depends on the intention of the photographer, obviously enough; how much warfare is carried on without surveillance, photography from satellite, aircraft etc. WW2 was full of it. You should know about the value of photography to bombing, Russ; the intention is seldom to waste ammunition. Why would present day urban fighters do any differently? Yes, prohibition is a pretty blunt instrument, but better than none at all, don't you think?
Anyway, having restrictions on photography of pretty obvious targets isn't really something that can be equated with living a life in fear - more with minor inconvenience to some photographers who may or may not be all that innocent. After all, the genuine photographer with a reasonable need can always apply for official permission which is by no means always denied.