Kilar leaves quite a positive legacy—in the five and a half years he spent at the start-up, he transformed it from a joke, nicknamed "ClownCo," to a digital content powerhouse. (Read More: Digital, TV Increasingly Hand in Glove: Pro.)
Last year the company generated nearly $700 million in revenue, up 65 percent over 2011. Its content library grew 40 percent and it generated more than $1 billion in revenue for its content partners. Its premium subscription option—which makes the app available on TVs and mobile devices—has been on fire. Kilar said in his farewell blog that it has added over 200,000 new subscribers in the past 7 days alone, a new record.
What now for the company?
There has been speculation that News Corp. or Disney would buy out the other company's stake. The two media giants have divergent visions for the company's future—Disney's more committed to the ad-supported Hulu.com, while News Corp is more interested in the paid Hulu plus app.
And the rise of "TV Everywhere" apps, which give cable and satellite TV subscribers access to their library of content from wherever they are, raise questions about what purpose Hulu serves for people who are not cutting the cord, a trend that its media giant parents certainly don't want to encourage. One idea: have Hulu serve as the universal authentication portal for all cable and satellite TV companies' TV everywhere options. (Read More: The Future of TV Is the Internet: Roku CEO.)
Who will replace Kilar?
There is one likely candidate: veteran digital media executive Ross Levinsohn. He's been scouting out his next move after leaving his position as interim Yahoo CEO when Marissa Mayer took over.
—By CNBC's Julia Boorstin; Follow her on Twitter: @JBoorstin
Note: Comcast is the majority owner of NBC Universal, the parent company of CNBC and CNBC.com.