In an interview with WSJ's Kevin Delaney, Groupon and LinkedIn investor Marc Andreessen insists that the recent popularity of tech companies does not constitute a bubble. He also stressed that both Apple and Google are undervalued and that "the market doesn't like tech.

In his excellent essay in the Wall Street Journal Mr. Andreessen points out three major challenges new companies are facing in today's economy:

"First of all, every new company today is being built in the face of massive economic headwinds, making the challenge far greater than it was in the relatively benign '90s. The good news about building a company during times like this is that the companies that do succeed are going to be extremely strong and resilient. And when the economy finally stabilizes, look out—the best of the new companies will grow even faster.

Secondly, many people in the U.S. and around the world lack the education and skills required to participate in the great new companies coming out of the software revolution. This is a tragedy since every company I work with is absolutely starved for talent. Qualified software engineers, managers, marketers and salespeople in Silicon Valley can rack up dozens of high-paying, high-upside job offers any time they want, while national unemployment and underemployment is sky high. This problem is even worse than it looks because many workers in existing industries will be stranded on the wrong side of software-based disruption and may never be able to work in their fields again. There's no way through this problem other than education, and we have a long way to go.

Finally, the new companies need to prove their worth. They need to build strong cultures, delight their customers, establish their own competitive advantages and, yes, justify their rising valuations. No one should expect building a new high-growth, software-powered company in an established industry to be easy. It's brutally difficult."