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The Ben Silverman experiment at NBC is now officially over.

The co-chairman of NBC Universal Entertainment, will leave the network before the fall season starts to take on a new job with IAC/InteractiveCorp. He will be replaced by Jeff Gaspin, the current leader of NBCU's cable department.

It's not clear if Silverman decided to leave NBC, if NBC wanted to part ways with him, or if it was more of a mutual decision. But one thing was clear ... there was not much to write home about on NBC over the last couple of years.

Where typically, network heads have hits and misses, Silverman was mostly misses. In the science-fiction genre it was most apparent. Although the decision to commission "Bionic Woman" was pre-Silverman, the studio head decided to follow up on that failure by reviving yet another classic genre show in the same exact time slot: "Knight Rider." That show, however, never connected with audiences, and barely lasted the season even after a revamp.

Then other shows, like the critically acclaimed "Kings," was bumped to a practically burn-off schedule from the start, and is on its way to being cancelled. That didn't really resonate well with genre fans as well as those who were able to find and fall in love with the show that starred Ian McShane and "Star Trek: Voyager" alum Susanna Thompson.

And let's not forget "My Own Worst Enemy."

On top of that, some of NBC's previously most popular shows have been run into the ground, including "Heroes," which had a panel at San Diego Comic-Con where people left less-than-enthused, according to reports.

There were some other non-genre head-scratchers as well, including the abandoning of the 10 p.m. timeslot to Jay Leno (which could still somehow be a long-term success), as well as a variety show that once starred Rosie O'Donnell.

NBC finished the 2008-09 season fourth among the major networks in total viewers and in key advertising demographics behind Fox, CBS and ABC.