Qualcomm's mobile team successfully maneuvering to kill Qualcomm's ARM server group when the server group looked like it was going to become very politically powerful because it would've had the highest performance ARM server part available and had large sales lined up at FB, etc.: https://www.patreon.com/posts/20571244 MS Office killing NetDocs basically Google Docs but created in 1997: https://twitter.com/danluu/status/790599349491212288. Also, NetMeeting (Zoom with whiteboard and stuff, '96): https://twitter.com/danluu/status/1572839354434977795?s=20
That thing that happened with GChat / Hangouts / Google+: https://twitter.com/danluu/status/1504567918746431492. More generally, all sorts of weird stuff getting tied to Google+, with threats to careers of people who didn't get in line: https://twitter.com/danluu/status/1122617702080581632 Similar story, but on the infra side, for a migration that probably doubled the server infra cost of a $100B+ company and caused a huge amount of re-write churn (this decision later flipped around and is now causing re-write churn the other direction).