Amazon's bestseller list was recently assaulted by a 24-year-old debut novelist, with a ready-made audience creating unprecedented demand for her book. If you're a teenage girl or YouTube expert you'll know who we're talking about by now. Zoe Sugg, aka Zoella, is a YouTube personality with 6.5m subscribers - the kind of audience other authors would kill for. And this audience has helped Sugg's novel, Girl Online, reach the top of the Amazon book chart.

Image: The Independent

This is good news for book lovers - anyone who loves to rant that the youth of today are more interested in their smartphones than reading a book will be disappointed by Girl Online's bestseller status.

But it's also a warning to anyone hoping to become YouTube famous. Yes, Zoella has a deal with YouTube that helps her make videos in return for advertising revenue, but her career rests on more than talking to a camera about beauty tips.

This isn't the first alarm bell to ring when it comes to YouTube celebrity. In our next post we'll look at Jason Calacanis's decision to terminate his YouTube partnership and what it means for the channel.