They didn't have a whole lot of competition, and their prices raised. Many people got angry with how expensive things were costing. Hackers and Crackers took a stab at modifying their hardware and software. The communitity of people who were making mods grew so much, and so close together, they eventually formed the Crossbones Exchange. When ULP enacted laws giving the Corp more power, they came up with their Declaration of Technological Independance.
That declaration is said to mark the beginning of the Cyberpunk Age.
With hackers and crackers arming themselves asserting that it's their right to spread technology through the verse, the UNIPOL was concerned that they would be unable to fullly enforce the cracking and modding laws that had been enacted. The advent of high bandwidth, intersystem connections known as The Grid, this technology was being spread at a pace that had never before been seen. With some additional influence from the Ultima Corp, the United League of Planets were influenced the creation of the Copyright Defense Act. From there, McKay created his own enforcement agency, the Ultima Corps, and armed them well.
Now, the Corpers and the Crossbones Exchange are in a constant war. Ultima Engineering creates a product, releases it. The Exchange cracks or mods it. The Corper Corps does what they can to enforce the law, and the Crossbones defend themselves. Similar battles are being fought elsewhere. Ultima Cryptography creates an encryption scheme, the Mathack group breaks it. Then guns get involved again. There are even rumors of battles going on at The Library.