Advertising clients are “really worried” about their promotions featuring alongside “extreme content” on Twitter Inc.'s platform, and its new owner must address moderation concerns, advertising guru Martin Sorrell said. 

A slew of advertisers including Volkswagen AG, Europe's largest carmaker, Pfizer Inc. and General Mills Inc. have said they're pausing spending on the platform while they wait to see how it evolves under billionaire Elon Musk's ownership.

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Musk must also “staunch the flow” of good people leaving his company if he wants to achieve a turnaround, the S4 Capital Plc executive chairman told Bloomberg Radio.

Sorrell's the latest executive to offer Musk advice. Former T-Mobile US Inc. Chief Executive Officer John Legere advised Musk in a Tweet to stop “managing daily business, and “content moderation” and then support product/technology.” Legere suggested that he could run Twitter instead. Musk responded, “No”.

Hi @elonmusk ,maybe I should run @twitter 🤔You can stop managing daily business, and “content moderation” and then support product/technology, let someone else “run” @Twitter .I'm expensive but so is what you paid for twitter (p.s. please be leadership example of how to tweet)

— John Legere (@JohnLegere) November 13, 2022

As well as cuts to about half of the workforce, a number of senior staffers have quit Twitter since Musk bought it, including three of its top privacy and security officials. Bloomberg reported the company has also asked some fired workers to come back.

The Twitter CEO's goal of increasing revenue, with advertising making up a lower proportion, however, is “wholly possible” as long as he fixes those two issues, Sorrell said. Ultimately, “don't bet against him.”