THE boom in digital entertainment — interrupted by the recession and the credit freeze — has returned to Hollywood. Almost daily, it seems, another start-up pops up to proclaim how it will revolutionize movies or television.

On May 10 came word of i-Trailers, a new company devoted to movie advertising on the Web and mobile devices. On May 11, Diva Mobile declared itself the entertainment industry’s “first cross-platform solution for video-on-demand” services. Arriving on May 13 was SulSet.com, a site promising to stream live, behind-the-scenes video from movie sets for a one-time $9.99 fee.

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