To take on YouTube. I’d be surprised if they impacted YouTube usage at all:

A video-sharing website intended to challenge the dominance of YouTube is to be named “Hulu” and will have the commercial weight of News Corporation and NBC behind it.
The two global media organisations announced the name today, saying they wanted something which sounds “inherently fun”.
Supported by advertising, the free-of-charge site will allow users to watch complete episodes of popular television shows from NBC and News Corp’s Fox network such as 24, The Simpsons and House.
[…]
Initially planned to launch over the summer, the site’s debut has gradually been pushed back. In a statement, Mr Kilar said operations would begin in October for invitation-only trials.
In addition to television shows, a selection of movie content will be available on Hulu including hits from News Corporation’s 20th Century Fox studio such, as The Devil Wears Prada and Borat.