The OpNet was a product of the Nova Age. It was created (indirectly) by a nova, destroyed by two other novas and (like so many nova-created technologies that survived the Aberrant War) remade with much of its functionality traded for safety.
In January of 2002, the nations of the world began to replace copper and fiber-optic cable with wireless networking and advanced synthetic-eufiber optic cable, along with new data-transfer protocols. The combination of optic cable and networking came to be known as "OpNet" over the three years it took to completely replace older systems, and it offered a 700% increase in bandwidth over the technologies available at the time.
The OpNet not only replaced the Internet and conventional telephony (both land-line and cellular), it absorbed older media as well. NBC's Will and Grace was the first program to take advantage of the OpNet's potential; in 2002, NBC and the show's producers put the program up for any-time viewing and added elements of audience interaction. Within a decade, the idea of "prime time" programming was all but extinct, and the idea of having to view a program on its first-run was reserved mainly for XWF pay-per-views.
In 2061, at the height of the war between baseline humanity and its quantum-charged children, the Terat known as Synapse was ambushed by a Taint-maddened Mungu Kuwasha. The two computer-masters fought for hours, inside the OpNet, trashing systems across the planet. Ultimately, Synapse (who'd been effectively living in the OpNet for over half a century) gained the upper hand and led his assailant into a deathtrap, but the dying Kuwasha unleashed an "electro-optical pulse" that destroyed the OpNet and set the stage for the Earth Strike Ultimatum. The idea of aberrant fighting aberrant didn't fit with the humans-versus-aberrants narrative of later historians, so the official explanation for the electro-optical pulse was that Kuwasha had wanted to see if he could destroy the OpNet.
By the 2120s, the OpNet had been somewhat restored, but even the best access (that of universities and governments) could be charitably described as limited. Moreover, fear of another electro-optical pulse's effects meant that only the most confident users networked their computers, or connected those networks to the OpNet in their entirety. In addition, the revised OpNet now carries a powerful failsafe - every main OpNet node is wired with explosives that are capable of destrying it completely. The failsafe can be triggered in one of two ways - by the command of the node administrator, or by a deadman's switch set to activate upon the cessiation of vitals of the node administrator.