If a packet can be delayed and copied, then the agents have an advantage on reacting to the information contained in the packet. All that is required is that the router software recognizes a special code in the packet, and delays it according to the value in the code. Then you set the router to delay packets from certain locations. The user won't see the delay, since it's not that long. But it was long enough for the agents to monitor what was going on, and react to the information while it is still active.
It wasn't hard for the FBI agents to modify their router box to include those delay packets. Each time they connected to an ISP, they installed the router delay software. And conveniently 'forgot' to uninstall it when they were done.
The packet sniffing software was a big hit with the FBI brass. The software and techniques used easily spread to just about every FBI office in the country. A few copies got out to law enforcement agencies in other countries. Those countries didn't have the First Amendment to worry about.
The packet delay software was like a virus. It quickly spread throughout the world through the Net. The software was compiled, so the source code was protected. But there were some global intelligence agencies that had some smart geeks out there, and it didn't take long for the source code to be uncompiled, and modified for their own use.
Soon, there were copies of the router delay software on just about every major ISP in the world, and most of the minor players also. It was such a useful tool that it got overused.
And that caused the Problem.