The FBI believes it can have it both ways: that it can open systems to its eavesdropping, but keep them secure from anyone else's eavesdropping. That's just not possible. It's impossible to build a communications system that allows the FBI surreptitious access but doesn't allow similar access by others. When it comes to security, we have two options: We can build our systems to be as secure as possible from eavesdropping, or we can deliberately weaken their security. We have to choose one or the other.
This is an old debate, and one we've been through many times. The NSA even has a name for it: the equities issue. In the 1980s, the equities debate was about export control of cryptography. The government deliberately weakened U.S. cryptography products because it didn't want foreign groups to have access to secure systems. Two things resulted: fewer Internet products with cryptography, to the insecurity of everybody, and a vibrant foreign security industry based on the unofficial slogan "Don't buy the U.S. stuff -- it's lousy."
In 1994, the Communications Assistance for Law Enforcement Act mandated that U.S. companies build eavesdropping capabilities into phone switches. These were sold internationally; some countries liked having the ability to spy on their citizens. Of course, so did criminals, and there were public scandals in Greece (2005) and Italy (2006) as a result.
In 2012, we learned that every phone switch sold to the Department of Defense had security vulnerabilities in its surveillance system. And just this May, we learned that Chinese hackers breached Google's system for providing surveillance data for the FBI.