As you've read in some of the comments to the video below, a number of people have experienced real problems with official persecution of acts of photographing in the U.K. Same thing here in the U.S. It's not a problem for you if you've never had problems, but I think the core of it is that you might get hassled and threatened now, sometimes by law enforcement personnel who might not even know what the laws are. We're simply less secure photographing in public than we used to be.
The problem for photographers as I see it is twofold. First, the public has gotten into its collective consciousness the harebrained notion that taking a picture is somehow "suspicious" behavior that might need to be reported to some authority (which then is obligated to respond), and second, the fact that it gives an excuse to belligerent people who are looking to create confrontations anyway. A friend privately told me of an experience he had of being confronted by the bouncer of a club/restaurant after taking a picture of the place from across a public street. What right has such a person (the bouncer) to make such an assault? None whatsoever, but that didn't protect my friend. Personally I got hassled when I was a photographer in D.C. a number of times, the worst incident while taking some pictures of a bunch of bike messengers who used to congregate on DuPont Circle after their shifts were over. Photographers getting hassled is nothing new; what's new is that the recent, allegedly "anti-terrorism" laws and attitudes are giving license to people with badges and in uniforms to engage in the same sort of hassling and confrontation that we've always been subject to--but that we used to not have to worry about from that particular sector. Since officials and law enforcement personnel have more power, including the power to clap you in cuffs and zap you with a Taser and detain you at the local jail, it's ratcheted our potential anxiety up to another level.
The bottom line is that taking pictures in public is not a hostile act. There has been no study that I've ever been able to find that reliably links the act of photographing with terrorist activity--I'm not aware of any case where a photographer who has been detained has turned out to be a terrorist, or, the other way around, a case where a terrorist was proven to have been out taking pictures in advance of some heinous act. There is just no link. Plus, there's the obvious problem of accurate correlation. Millions of people take pictures, so how do you distinguish picturetaking with malicious intent from just plain old picturetaking? The answer is, you can't. But it just "seems reasonable" to ordinary people to suppose that terrorists "must" case out their targets with cameras prior to bad acts.
This shibboleth has been taken up by the media, which reports picture-taking as a supposedly "contributing" fact when making some baseless report of suspicious activity that later turns out to have been nothing. Several years ago there was a case where two brothers and their cousin, all of Middle-Eastern extraction, were captured crossing the Mackinack Bridge in Michigan with a van containing more than a thousand cellphones. The news reports were hysterical, clearly implying a plot to blow up the bridge. One of the "facts" reported in support of this was that the men had "a number of photographs" of the bridge in their possession, taken while crossing the bridge.
I followed the case because I have a relative who was alarmed by it. I pointed out to her that these sorts of reports were common in the media, probably because the government was trying to make the public fear terrorists as a means of enlisting support for its "War on Terror," and that most if not all of the hysterical "terrorist plot" reports, if you take the trouble to follow them to their conclusions, turn out to be baseless. That part doesn't get reported, certainly with anything like the blanket coverage of the initial alarm. Anyway, I followed the case of the three "terrorists" who were dead certain to be plotting to blow up the bridge. It turned out they were three schmucks from Texas who were trying to capitalize on regional differences in cell phone prices. The pictures they took crossing the bridge were taken for the exact same reason almost everybody who crosses the bridge takes pictures--because it's an awe-inspiring structure (for quite a while it was the longest suspension bridge in the world) with spectacular views of the Straits. The three men with the cellphones took pictures of the bridge, it was true. What's also probably true is that almost everybody who crosses the bridge for the first time and has a camera handy takes pictures of it too! If you had to arrest everybody who took pictures while crossing the bridge you'd have to arrest half the people who come across. In any event, no evidence of malice on the part of the three Texans could be found, and charges against them were quietly dropped. But of course that didn't get reported in the news nearly as widely. (And the case is still being batted around the internet as "evidence" of terrorism plots.)
The interesting aspect of this case, and the reason I mention it, is simply the fact that the news media in its initial flurry of alarm reported the fact about the pictures of the bridge in the mens' possession as if that were actual proof of bad intent. It wasn't--it couldn't have been, because, as was later proven, the men didn't have any bad intent--but that's the public perception, that terrorists take pictures, and that, therefore, someone having taken pictures amounts to circumstantial evidence against them.
It's this perception that photographers need to fight--the very idea that there's any connection in the first place between photographing and terrorism. There just isn't. It's a common notion, but a false one. Even if there was a connection, you couldn't distinguish the bad actors from all the innocent ones anyway. But the link itself is the misperception. That's what I think we need to continually try to assert in defense of our rights and actions.