The only thing that can stop Google or Facebook is Amazon, says Roger McNamee

Google and Facebook have remarkably resilient business models as they scoop up an ever-greater percentage of the online advertising market. But there's one threat: Amazon's eventual dominance of retail.

That's what Elevation Partners Co-Founder Roger McNamee told CNBC on Monday.

"Eventually they're going to be such a large percentage of the retail business that when Facebook and Google are going to try to sell ads the only guy on the other side is going to be Amazon," said McNamee.

He added, "If you're wondering what the limit function is on Google's model or on Facebook's model it's Amazon getting a large enough share of retail to be able to say, you know I like that price but I'm gonna put two zeros in before the integer value, and cut the price by 99%," he said. "They will have that power eventually."

McNamee says Amazon's potential dominance in the retail sector is only one part of the equation, the other arguably more important part, he says is the company's data. "Amazon is hosting all of the best applications, they have all the best intelligence that everybody wants," said McNamee.

"How long would it take them to go from zero to number one in e-mail, for example? How long would it take them if they decided to make security a really, really, really important element of what they're doing?" he said.