Elevation Partners' co-founder told CNBC's "Squawk Alley" on Wednesday that the business model these companies have adopted has serious consequences for users and the public at large.
"If you're trying to maintain attention, if you're fighting for a share of 24 hours in peoples' lives, the big issue is you have to keep escalating. It turns out the way you keep people's attention is you either scare them or you make them angry." He compared the effects of Google and Facebook to nicotine, alcohol or heroin.
Still, the people running the companies aren't "terrible" people, McNamee said.
"I don't think they are consciously doing bad things. I think what happened was they each adopted an advertising-based business model that essentially encouraged engagement," McNamee said.