Microsoft buying Salesforce called a terrible idea

It would be a terrible strategic mistake for Microsoft to acquire Salesforce, Roger McNamee, the co-founder of Elevation Partners, said on Wednesday.

"If I were a shareholder of Microsoft, I would be sending a note to the board of directors going, 'Please do not do this,' " McNamee said.

Salesforce, which has a market capitalization of $48.7 billion, is already too big. Microsoft should be building in house instead of acquiring a company such as Salesforce, said McNamee during CNBC's "Squawk Alley."

"They should be building things internally, and they have lots of opportunities to do that," said McNamee.

Read More Here's why Microsoft could buy Salesforce

Marc Benioff, chairman and chief executive officer of Salesforce.com Inc. (left), speaks with Tony Prophet, vice president of Windows marketing at Microsoft Corp.

Noah Berger | Bloomberg | Getty Images

To Microsoft, Salesforce's culture might be more appealing than the products.

Yet, since Microsoft isn't looking for a new CEO, the company is certain not to benefit from the culture built by Marc Benioff.

"I think in fact a large number of people would leave right away and they'd have all the products and the products would be of some value, but I don't think you can justify 50 or more billion dollars to acquire a company at that stage," said McNamee.