NYPD and Cell Phones During Terrorist Attacks

According to a Wired.com post from yesterday, it has become apparent that New York City police officials - including Commissioner Ray Kelly - believe that jamming cell phones during a terrorist attack may save lives and break up coordination. Kelly cites the attacks in Mumbai from last month as an example (the terrorists used cell phones for contact). What are your thoughts on this? Is the government overstepping boundaries here, or is the suggestion necessary?