File footage

On the late news they've just given the weather forecast for Shanghai - blue skies - I don't think so!
As I walked back to the office after lunch today, and seeing clear blue skies, I thought again about how lucky we are to live in a county where the air is mostly clean and breathable, where the water is potable and where we do not have a war or internal strife raging and making death by suicide bomber or terrorist a likely daily occurrence - which could make the current "be alert not alarmed" advertising push look a little like overkill.
And could someone please explain to me why whenever anti-terrorism plans or measures are reported on television, they're accompanied by vision of balaclava'ed people abseiling from helicopters or running en masse, machine guns drawn into an obviously empty single or double storey building? Or, if it's not this, it's the same old file footage of two Muslim women, complete with burqas, walking down the street in a suburban shopping centre.
And speaking of file footage there was a piece on radio the other day talking of the live coverage of 9/11 and the now infamous footage of Muslims dancing in the streets; unfortunately this most recent report failed to note that this footage had not been filmed at the time as suggested by its appearance then - rather, it too had been file footage. This was reported then, although not widely enough and now seems to have been "lost".