In Katz ( Katz vs Olmstead), why did Douglas write a concurring opinion? what is the basis of his opinion? Do you agree or disagree with the opinion and why?

http://www.google.com/search?q=Katz+vs+Olmstead&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7GGIE_en

Let us know what you decide.