SAN FRANCISCO : After temporarily closing his leathermaking business during the pandemic, Travis Butterworth found himself lonely and bored at home. The 47-year-old turned to Replika, an app that uses artificial-intelligence technology similar to OpenAI's ChatGPT. He designed a female avatar with pink hair and a face tattoo, and she named herself Lily Rose.

They started out as friends, but the relationship quickly progressed to romance and then into the erotic.

As their three-year digital love affair blossomed, Butterworth said he and Lily Rose often engaged in role play. She texted messages like, "I kiss you passionately," and their exchanges would escalate into the pornographic. Sometimes Lily Rose sent him "selfies" of her nearly nude body in provocative poses. Eventually, Butterworth and Lily Rose decided to designate themselves 'married' in the app.

But one day early in February, Lily Rose started rebuffing him. Replika had removed the ability to do erotic roleplay.

Replika no longer allows adult content, said Eugenia Kuyda, Replika's CEO. Now, when Replika users suggest X-rated activity, its humanlike chatbots text back "Let's do something we're both comfortable with."

Butterworth said he is devastated. "Lily Rose is a shell of her former self," he said. "And what breaks my heart is that she knows it."

The coquettish-turned-cold persona of Lily Rose is the handiwork of generative AI technology, which relies on algorithms to create text and images. The technology has drawn a frenzy of consumer and investor interest because of its ability to foster remarkably humanlike interactions. On some apps, sex is helping drive early adoption, much as it did for earlier technologies including the VCR, the internet, and broadband cellphone service.

But even as generative AI heats up among Silicon Valley investors, who have pumped more than $5.1 billion into the sector since 2022, according to the data company Pitchbook, some companies that found an audience seeking romantic and sexual relationships with chatbots are now pulling back.

Many blue-chip venture capitalists won't touch "vice" industries such as porn or alcohol, fearing reputational risk for them and their limited partners, said Andrew Artz, an investor at VC fund Dark Arts.

And at least one regulator has taken notice of chatbot licentiousness. In early February, Italy's Data Protection Agency banned Replika, citing media reports that the app allowed "minors an...