David Kohl, the top sales executive at Vevo, has left the music video company. Kohl joined Vevo in 2009 as executive vice president of sales and customer operations to get the fledgling music brand off the ground.

A Vevo spokesperson confirmed Kohl's departure, but declined to comment.

The company has retained executive search firm Spencer Stuart to seek a new head of sales.

Ad sales have been the backbone of Vevo’s revenue, which in turn have made the company one of many artists’ largest sources of supplemental revenue. In 2012 alone, Vevo paid $100 million to artists and other rights holders – double what the company paid in its two previous years, and a result of higher cost per thousand viewer rates, or CPM, sold to advertisers in foreign territories. In the U.K., for example, Vevo grew its ad CPMs from £2 at the beginning of 2012 to more than £20 by the end of the year.

Billed as a Hulu for music videos, the joint venture between Universal Music Group, Sony Music and Abu Dhabi Media has become one of the most trafficked video destinations on the Web over the past four years—largely on the back of YouTube where Vevo serves as the default destination for music video searches on YouTube.

Vevo drew close to 50 million unique viewers in February, according to comScore. During Kohl's tenure, Vevo has attracted hundreds of top brand advertisers while building an eight-figure global ad business. "This is crazy to me," said one source close to the situation. "There's no way you could argue with their growth."

But according to those with first-hand knowledge of the site's business model, Vevo has serious challenges. For every dollar earned, half must be shared among the various record labels and a third goes to YouTube, according to All Things D. That’s led Vevo to flirt with ditching YouTube for Facebook, consider joining forces with MySpace, or negotiating a new partnership with YouTube that would include a $50 million investment in Vevo from Google.

Last month, Vevo rolled out the linear Web network Vevo TV, a clear sign that the company is looking to lessen its reliance on YouTube by broadening its reach. There's also been some speculation that Vevo might explore building out a "media content network" on YouTube. Under that scenario, Vevo could also handle ad sales for other music content producers on YouTube.

Prior to joining Vevo, Kohl headed up Nokia's mobile sales group in the U.S., Latin America, Europe and Asia. Before that, he was senior vice president of sales for Viacom's MTV and Comedy Central channels.

The timing of Kohl's departure is awkward, given that Vevo's NewFront presentation to present its content to advertisers is just a few weeks away. A Vevo spokesperson said the event, set for May 2, remains on track.

Additional reporting by Billboard's Andrew Hampp and Alex Pham.