The Quantified Self (QS) movement is comprised of people who use various recent technologies to accumulate detailed knowledge of what their bodies are doing — how they’re breathing, how much they walk, how their heart-rate varies, and so on — and then adjust their behavior accordingly to get the results they want. This is not surveillance, some QS proponents say, it’s the opposite: an empowering sousveillance.

But any technology that I can use for my purposes to monitor myself can be used by others who have power or leverage over me to monitor me for their purposes. See this trenchant post by Nick Carr:

One can imagine other ways QS might be productively applied in the commercial realm. Automobile insurers already give policy holders an incentive for installing tracking sensors in their cars to monitor their driving habits. It seems only logical for health and life insurers to provide similar incentives for policy holders who wear body sensors. Premiums can then be adjusted based on, say, a person’s cholesterol or blood sugar levels, or food intake, or even the areas they travel in or the people they associate with — anything that correlates with risk of illness or death. (Rough Type readers will remember that this is a goal that Yahoo director Max Levchin is actively pursuing.)

The transformation of QS from tool of liberation to tool of control follows a well-established pattern in the recent history of networked computers. Back in the mainframe age, computers were essentially control mechanisms, aimed at monitoring and enforcing rules on people and processes. In the PC era, computers also came to be used to liberate people, freeing them from corporate oversight and control. The tension between central control and personal liberation continues to define the application of computer power. We originally thought that the internet would tilt the balance further away from control and toward liberation. That now seems to be a misjudgment. By extending the collection of data to intimate spheres of personal activity and then centralizing the storage and processing of that data, the net actually seems to be shifting the balance back toward the control function. The system takes precedence.  

Do please read it all.