The article in the link below addresses a possible "do not track" law. The article also provides insight into the type of data that is being collected. "Behavioral tracking" and "behavioral targeting" are buzz words that are sometimes associated with this type of tracking activity.
<http://www.nytimes.com/2007/11/01/technology/01Privacy.html?_r=3&ref=technology&oref=slogin&oref=slogin&oref=slogin>