After the dotcom crash I looked for some safe haven outside of the industry, and found a landing place at a global fiber optics networking division of an energy trading company called Dynegy. Sounded safe! A month after joining they backed out of their planned buyout of their largest competitor Enron. Apparently this Enron thing was cooking their books. Enron sued Dynegy, Dynegy countersued, and started laying people…
Enron created a "bandwidth marketplace", that is, a commodity market like there is for energy where providers can bid for data transit between locations. Then they estimated all the value of all the future trades on that market based on some very optimistic assumptions, estimated all their own future profit as the market maker using even more optimistic assumptions, and marked all that hypothetical profit to market and immediately recognized it as profit on their books.
It was tens of billions of dollars. Despite the fact that a "bandwidth marketplace" doesn't actually make sense (data transfer is a lot less fungible than energy, and there are usually only very few possible competitors for any route), and even if it had made sense, they couldn't have hoped to secure anywhere near the cut they assumed, and even if they had, the bottom was going to fall out of the market because people kept coming up with new and exiting ways to move more data on the same fiber, leading to massive overcapacity.