By Gordon Corera
BBC News security correspondent
The recent spate of reports on bugging and intercepting communications has revealed how little people really know about the level of surveillance they are under.
Different types of surveillance have different types of oversight
Even MPs, it seems, are unsure whether they can be bugged or not, or what the rules exactly are.
It is widely known that Britain is the most watched Western society, but what does that actually mean? Who does it and how? And who keeps track of this - or to put it another way, who watches the watchers?
Firstly, it is important to be clear that there are many different types of surveillance under the law, each of which is conducted by different agencies and with different forms of supervision.
Intrusive surveillance involves the presence of an individual on private residential premises or in a private vehicle.
It also includes any surveillance carried out by means of a device - in other words a bug or a probe.
Directed surveillance is where an individual is followed around in public and their movements recorded.
Covert human intelligence sources involve using people going undercover to spy on other people.
Intercept refers to literally intercepting the communications of individuals whether by phone or on the internet - but not through a physical recording device in the place where they are speaking.
Different levels of authorisation apply to each of these activities. Intercept by intelligence agencies requires the approval of a minister.
Other activity can be carried out by organisations with only the approval of senior managers, although the Office of the Surveillance Commissioner does have the ability to scrutinise and reject surveillance activity.
Most of this activity is regulated by the Regulation of Investigatory Powers Act (Ripa).
Errors do occasionally happen, as revealed in surveillance and interception commissioners' reports but they maintain they are rarely deliberate and usually involve a phone number being wrongly transcribed.
The most recent interception commissioner report revealed that 474 local authorities are empowered to obtain communications data, of whom 122 used the power in 2006 making 1,694 requests.
Six fire services even asked for data. There were 1,088 errors involving communication data out of a total of 253,557 requests.
Then there is the now ubiquitous CCTV which is not always covered by Ripa since they are not hidden and not targeted at a particular individual.
The first use of video surveillance or CCTV in the UK is believed to have been a camera 1961 at a London railway station.
The contrast is clear if, as I recently did, you walk into the control room at a busy Tube station like Westminster.
Cameras now cover at least 98% of the station. Every time a gap in coverage is discovered, a way is found to close it.
Technology has been one of the key drivers of this process as it becomes possible to do more and more.
But it can also pose challenges. One of the biggest challenges for the eavesdropping agency GCHQ is to maintain its intercept capability in the face of rapidly evolving communications technology.
The capacity for surveillance will increase as technology develops
This relates in particular to the growth in internet-based communications and voice over internet telephony.
The director of GCHQ, Sir David Pepper, explained the significance of these changes to a parliamentary committee saying: "The internet uses a very different approach to communications in that, rather than having any sense of fixed lines like that, there is a big network with a number of nodes, but for any individual communicating, their communications are broken up into shorter packets.
"So whether you are sending an e-mail or any other form of internet communication, anything you send is broken up into packets.
"These packets are then routed around the network and may go in any one of a number of different routes because the network is designed to be resilient.
This (represents) the biggest change in telecoms technology since the invention of the telephone. It is a complete revolution."
A report from the Royal Academy of Engineering argued that as technologies for collecting and processing data develop rapidly, the changes for privacy will be significant and that much more needs to be done to think how to deal with this.
For instance there is the use of RFID tags - tiny wireless devices which can be read by remote sensors - they are now being used by shops to keep track of stock but can also be used as a tracking device.
As people are increasingly aware, a mobile phone can be used to track the rough whereabouts of an individual even if it is not being used.
Oyster cards on London Transport can also be used for surveillance and investigating people's movements.
Huge databases surrounding areas like DNA and identity cards also create concerns, particularly in the current context of instances of leaks and losses of sensitive data.
Some passengers in the US have found themselves falling foul of vast new watch lists if their name is similar to a suspected terrorist and have found trouble getting rid of the problem.
As technologies develop, the capacity for all forms of surveillance and data collection and management will continue to increase.
The challenge will be making sure oversight, accountability and public confidence are not left behind if those new powers are put to use.