YouTube will imminently launch a movie-on-demand service charging users to stream mainstream Hollywood movies off the world’s largest video sharing site, TheWrap has learned. The new service means a full-bore challenge to Apple’s iTunes service, currently the most powerful player in paid video streaming, and a welcome new revenue stream for Hollywood as home entertainment revenues continue their steep decline. The service may start as early as this week or next, and is expected to be announced soon by YouTube. Major studios including Sony Pictures Entertainment, Warner Brothers and Universal have licensed their movies for the new service, as have numerous independent studios, including Lionsgate and the library-rich Kino Lorber, according to movie executives with knowledge of the deals in place.