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YouTube is probably the most influential media business for a youth audience. But on this week's Tech Tent podcast, we ask whether Google is struggling to police its platform.

If you ask people my age what they think is the world's most important and powerful TV firm, they might suggest Fox, Netflix or perhaps even the ´óÏó´«Ã½.

But for anyone under 30, the answer could well be YouTube. They might even single out individual personalities who attract huge audiences to their channels, such as video gamer PewDiePie.

Chris Stokel-Walker is the author of YouTubers. His book examines the rise of this new generation of TV superstars, who earn huge sums through advertising and sponsorship.

He compares these influencers to 1950s news presenters such as Walter Cronkite, who addressed viewers in their homes each night, making them feel they had a personal connection.

"Marketers are really starting to wake up to that and realise that if they can get their products in front of these people, then they're selling loads," he says.

But an audience often made up of teenagers and young children is in thrall to a medium that could be far more addictive than old-fashioned telly.

The YouTube algorithm is designed to encourage people to keep watching for longer. It sometimes leads viewers to watch ever more extreme content.

The behaviour of some of these influencers on a largely self-regulated platform has raised concerns.

Logan Paul, whose YouTube channel has nearly 20 million subscribers, was forced to apologise after filming a body hanging in a Japanese forest.

PewDiePie, perhaps YouTube's biggest star, has come under fire for using anti-Semitic imagery as punchlines in jokes.

This kind of scandal has occasionally seen advertisers step back from YouTube. But generally the platform and its owner Google have faced a lower level of scrutiny over abusive content than Facebook or Twitter, when it has a bigger young audience than either of them.

Chris Stokel-Walker says Google tends to be reactive rather than proactive when it comes to cleaning up YouTube.

"They are taking each scandal as it comes and trying to fix things as and when they happen," he says.

YouTube may worry that cracking down on extreme content comes at a cost.

Google's disappointing advertising revenue growth this week was blamed in part by chief financial officer Ruth Porat on fewer than expected clicks on YouTube ads.

She said this reflected changes made last year which the company believed were "overall additive to the user and advertiser experience".

This was thought to be a reference to a tweak to the platform's algorithms, which made "harmful" - but compelling - content less likely to appear in the recommended videos feed.

YouTube has three constituencies - the users, the creators and the advertisers. Keeping them all happy while avoiding unfavourable publicity is going to be ever more challenging.