Yammer founder David Sacks created a stir in the tech industry when he recently offered his pessimistic opinion about the state of Silicon Valley on his Facebook wall. Forget a bubble; Sacks declared, the Valley is “coming to an end.”

Wednesday, on stage at TechCrunch Disrupt in San Francisco, Sacks had a chance to explain his statement (reposted here by TechCrunch).

“I’m not saying innovation is coming to an end,” Sacks said, “but the Internet ecosystem has changed… it’s not an early-growth forest anymore.”

The “forest,” as Sacks calls the Web sector, currently boasts a serious collection of large redwood trees--among them are brands like Apple, Facebook, and Google.

“What I’ve suggested entrepreneurs do is go to the edge of the forest,” Sacks told TechCrunch founder Mike Arrington.

This wasn’t Sacks’ first time in front of a TechCrunch audience. His company, enterprise social network service Yammer, launched in 2008 at TechCrunch50. Yammer was acquired in June by Microsoft for $1.2 billion dollars

VC Marc Andreessen took issue with Sacks' declaration about Silicon Valley. In a comment chain on Facebook, he rebutted Sacks' suggestion that the future of viable ideas in Silicon Valley can only come from big name companies.

“Human creativity is limitless,” Andreessen wrote. “Which doesn’t make it easy, but does mean the opportunity is unending.”

On stage, Arrington reminded Sacks that the impossible can (and will) be done--offering quotes from people who at one time argued that airplanes would never exist or that no one would ever want to watch a movie with sound. But Sacks stood by his statement. He predicted the disruption of television, which he said was inevitable, will come from a redwood tree before is comes from a recently planted spruce.