Bruce Schneier explains:
The FBI...has been given whatever vulnerability it used to get into the San Bernardino phone in secret, and it is keeping it secret. All of our iPhones remain vulnerable to this exploit. This includes the iPhones used by elected officials and federal workers and the phones used by people who protect our nation's critical infrastructure and carry out other law enforcement duties, including lots of FBI agents.
This is the trade-off we have to consider: Do we prioritize security over surveillance, or do we sacrifice security for surveillance?
The problem with computer vulnerabilities is that they're general. There's no such thing as a vulnerability that affects only one device. If it affects one copy of an application, operating system or piece of hardware, then it affects all identical copies. A vulnerability in Windows 10, for example, affects all of us who use Windows 10. And it can be used by anyone who knows it, be they the FBI, a gang of cyber criminals, the intelligence agency of another country -- anyone.
I understand the frustration of cops everywhere who see these troves of data that didn't exist 10 or 15 years ago just out of reach thanks to manufacturers' security measures. But it shouldn't take a security expert like Schneier to convince people that those features protect us more than they hurt us.