Twitter CEO Elon Musk threatened to sue Microsoft on Wednesday, accusing the software giant of illegally using the social media company’s data to train its artificial intelligence model.

Musk’s threat by tweet came after Mashable and other publications reported that Microsoft would drop Twitter from its advertising platform, which enables ad buyers to manage all of their social media accounts in one place.

“They trained illegally using Twitter data,” Musk tweeted. “Lawsuit time.”

Musk, who is also CEO of Tesla and SpaceX, often tweets about plans that never come to fruition, and no lawsuit appears to have been filed. Twitter’s press line didn’t respond meaningfully to a request for comment, and a Microsoft representative declined to comment.

Musk’s threat is the latest indication that data ownership is quickly becoming a fraught battleground in the generative AI rush. Big Tech companies are working to develop cutting-edge AI models like OpenAI’s GPT, and data owners are seeking to stop them or charge for use of their content.

Microsoft develops its own so-called large language models (LLMs) and sells access to OpenAI’s models. Microsoft invested $10 billion in OpenAI last year in an unusually structured deal. Musk was a co-founder of OpenAI before leaving its board in 2018, and has complained recently of the company’s move from a nonprofit model to a highly valuable business influenced by Microsoft.

LLMs like GPT require terabytes of data for training, much of which is scraped from websites like Reddit, StackOverflow, and Twitter. Training data from social networks is valuable because it captures informal, back-and-forth conversations.

As these new AI models move from research labs and universities into the corporate world, the owners of the data are starting to make demands.

For example, Reddit said earlier this week that it would charge companies for access to its programming interface used to feed the conversations among Redditors into AI training software. Universal Music Group also said this week that such training of artists’ music would represent “both a breach of our agreements and a violation of copyright law” in response to a viral video of a song that claimed to use AI to imitate the rapper Drake.

And stock photo database Getty Images is suing Stable Diffusion, alleging that the company copied its content to train its AI image generator.

Musk said in December that Twitter would “pause” OpenAI’s access to its database. He’s also announced plans to build his own large language model in one of his companies called TruthGPT.

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