Comment by boredguy8

If you have some time, read "Warrantless location Tracking" 83 N.Y.U.L. Rev. 1324 http://www.law.nyu.edu/ecm_dlv2/groups/public/@nyu_law_websi...

  A common step in police investigations today is to secure a court
  order tracking the movements of a suspect or anyone else whose 
  location the police believe useful. The flip side of this 
  powerful tool, though, is how revealing and intrusive it is. Few 
  people would be comfortable being followed by a police officer 
  all day, even if they did nothing illegal or even interesting. 
  Justice Brandeis once invoked the "right to be let alone,"  and 
  undetectable location tracking pressures the alone part: No one 
  is "let alone" if the police may, without notice or probable 
  cause, find out everywhere they go for a day or a month.

It's a good, if disturbing, read.