‘Microsoft did horrible things to Slack’: Salesforce CEO Marc Benioff warns OpenAI could be next

Salesforce

In a no-holds-barred interview, Salesforce CEO Marc Benioff has taken a sharp jab at Microsoft, accusing the tech giant of using unfair tactics to crush competition– first with Slack, and possibly now with OpenAI.

Benioff didn’t mince words. “Microsoft did horrible things to Slack before we bought it,” he said during a podcast chat with SaaStr CEO Jason Lemkin. According to him, Microsoft followed a “dark playbook” that seriously hurt Slack’s chances in the market and he’s worried the same thing could happen with OpenAI.

To understand the context, back when Slack was gaining popularity as a workplace messaging app, Microsoft launched its own rival, Teams, and bundled it for free with its Microsoft 365 suite. Slack called foul and filed a complaint with the European Union, arguing that the bundling gave Microsoft an unfair advantage. In 2024, Microsoft finally agreed to unbundle Teams, but the damage was already done.

Benioff said Microsoft’s tactics weren’t just aggressive, they were deeply unfair. “They were running their playbook and did a lot of dark stuff,” he remarked. He even compared it to the tech wars of the 1990s, when Microsoft was accused of crushing competitors like Netscape during the browser wars.

The Salesforce boss believes Microsoft is following a similar strategy today with OpenAI. While the two companies are officially partners — Microsoft has invested billions into OpenAI and uses its technology for products like Copilot — Benioff warned that the partnership could quickly turn into a rivalry.

“In the case of OpenAI, a partnership is gonna become a competition,” he predicted, hinting that Microsoft’s history of absorbing or outmaneuvering startups might repeat itself.

Interestingly, there have already been signs of tension. Recent reports suggest Microsoft may be exploring alternative AI models to power its services, potentially reducing its reliance on OpenAI.

Benioff’s comments serve as a public warning — both to OpenAI and the broader tech world — that trusting Microsoft too much could backfire.

“Microsoft is a company that wants to own it all, control it all,” Benioff said. “That playbook should get ripped up and thrown away.”