After Hours

Ten catastrophes: All-time worst tech industry executive decisions

John Opel, IBM: Not buying Microsoft during the PC-DOS/MS-DOS negotiations / Gary Kildall, Digital Research, not licensing CP/M to IBM

Information Technology, software and computer companies are certainly not without their share of poor executive decisions and mismanagement.  While dozens of notable examples could have made our list, these were by far the top top 10 worst in the history of the technology industry, causing many billions of dollars of lost revenue or resulted in the downfall of entire companies.

In the late 1970's, a small team within IBM began development of its legendary 5150 PC, which recently had its 30th anniversary. But to run this PC, IBM needed an operating system.
At the time, there was only one serious contender, Digital Research's CP/M, which ran on a number of early personal computers including the Apple ][, The Osborne and the Kaypro, all of which had substantial market share in a small but quickly growing industry.
In 1980, Under the direction of CEO John Opel, IBM attempted to contact Digital Research's founder and CEO, Gary Kildall, to license CP/M for use on the 5150 and other future PCs, but when negotiations failed, IBM went looking for another suitor.
Bill Gates, Steve Ballmer and Paul Allen at Microsoft, seeing an opportunity in the making, approached a tiny software company, Seattle Computer Products, which had an x86-compatible OS which used a similar command interpreter to CP/M called 86-DOS. Microsoft purchased the OS and perpetual usage rights, which they then re-christened as "DOS", for a mere $75,000.
After negotiating an almost unheard of non-exclusive licensing agreement with IBM, the company would be established as the leader in personal computer software for decades to come. 
Microsoft's MS-DOS would go on to sell tens of millions of licenses, and the software business for Windows and related follow-on products that Microsoft would generate which would build upon it would turn the company into an industry giant.
Digital Research could very well have had the same licensing deal and IBM could have imposed stricter licensing terms on MS-DOS, or could have purchased either of the two companies outright, giving the company an exclusive. But it was not to be. 
Digital Research's CP/M became an also-ran and the company eventually attempted to produce it's own DOS clone, DR-DOS, which although having a number of technical improvements over Microsoft's OS, was a dud. It was eventually sold to Novell, then Caldera and then later on became the property of SCO.
Eventually, the highly competitive MS-DOS based PC clone business made Digital Research's CP/M irrelevant and also would eventually force IBM to exit their own PC business in the late 1990s and early 2000's.