Government Doesn't Need Warrant To Search Cellphones

The US government allowed police to search cellphones without a warrant. Computers however can only be searched with a warrant.  Today's iPhone and other smart phones are far more sophisticated than personal computer only years ago.
 
Today's smart phones let government officials access much about one's life - perhaps as much as their PC?
  
What is the difference between smart phones and computers as the two devices start looking more and more like each other?

At least those going after patent infringers have one more way of catching intellectual property thieves.  It's now harder for patent infringers to hide their illicit activity behind smart phones as they can be checked without a warrant. This is one positive aspect notes Innovation Institute, LLC.

http://www.newscientist.com/blogs/onepercent/2011/02/whats-the-difference-between-a.html