Where’s all my CPU and memory gone? The answer: Slack
Found on Medium on Thursday, 27 July 2017

CPU and memory usage increases linearly as you add more accounts to your Slack desktop client. As a result, I believe the growing trend to use Slack to be part of multiple communities is seriously flawed until Slack resolve this problem.
What a total waste of resources for an overhyped fancy IRC client used by hipsters.