It's not a crime so why harrass us?

You wouldn't think taking a picture is a crime would you? In fact unless you're taking it in a restricted area it isn't, though a lot of people including professional photographers are having a hard time getting the police to believe this. Some areas like military bases would be fairly obvious, some however aren't and are in fact tourist attractions.
The problem lies in Section 44 of the Terrorism Act 2000.

Authorisations under section 44 of the Terrorism Act 2000 confer extraordinary powers of stop and search. They can be made where expedient for preventing acts of terrorism.

The areas are chosen based on their likelihood of being a terrorism target. More than 100 exist in London alone, covering areas such as the Houses of Parliament, Buckingham Palace and other landmarks. Every train station in the UK is covered by a Section 44 order. However it has been used to prevent pictures being taken of policemen too as well as the plastic plods.

Independent

Police have been accused of misusing powers granted under anti-terror legislation after a series of incidents, ranging from the innocuous to the bizarre, in which photographers were questioned by officers for taking innocent pictures of tourist destinations, landmarks and even a fish and chip shop.
Police are allowed to stop and search anyone in a designated "Section 44 authorisation" zone without having to give a reason. But amateur and professional photographers have complained that they are frequently being stopped and treated as potential terrorists on a reconnaissance mission. Last night the Government's independent reviewer of anti-terrorism laws warned police forces to carefully examine how they use the controversial legislation.
A BBC journalist was stopped and searched by two police community support officers as he took photographs of St Paul's Cathedral. Days earlier Andrew White, 33, was stopped and asked to give his name and address after taking photographs of Christmas lights on his way to work in Brighton.
And in July Alex Turner, an amateur photographer from Kent, was arrested after he took pictures of Mick's Plaice, a fish and chip shop in Chatham.

It's being spun as a lack of training in the complex legislation, but from where I stand it's being used as a tool to intimidate the public and make them afraid of the state and its servants. 13 years of Labour have eroded our civil rights to the stage where people are becoming afraid of their own shadows.
Labour have used Anti-Terror legislation to evict elderly members of the Labour Party from their own conference for heckling a government minister, or arresting grandmothers on peaceful demonstrations against nuclear power, or the Met in 2008 using stop and search powers to search 58 children aged nine or younger. Indeed last year a total of 2,331 children aged 15 or under were stopped by Met officers using terrorism powers in circumstances where there is absolutely no evidence of children in this country being involved in acts of terrorism!
RIPA, recycling officers, council snoopers, on the spot fines for feeding ducks, it's like they're goading us into civil disobedience and yet amazingly still, people do nothing, they sit at home watch X Factor and when pressed come out with ridiculous platitudes of "Having done nowt wrong I've nowt to fear!"

We're sleepwalking into a police state and when you tell people they simply don't believe you, it's for our own good, to prevent terrorism they say, it couldn't happen to me and yet the evidence is mounting that it can and will.

In the film V for Vendetta, V makes the statement that "there is something terribly wrong with this country, isn't there?"
And there is, but unlike in the movie, no one's listening!

As V also said, "People should not be afraid of their government, governments should be afraid of their people."

And this government is acting as if it's very afraid, yet so are the people, until we lose the fear of authority we have had ingrained into us, these things will carry on happening and the abuses will continue until we are prepared to say enough is enough.