But the reserved, slow and steady approach has long frustrated some investors and employees, who believe that it has neutered growth, according to interviews with more than a dozen people who have worked with or for the company. Many of those people spoke on the condition of anonymity because they were not authorized to speak about the company’s private affairs.

Matt Novak, a partner at All Blue Capital, said his firm was trying to sell its stake in Pinterest, which the firm acquired on the secondary market, because it had not lived up to its potential.

“If they don’t keep up, they very quickly become prehistoric,” said Mr. Novak, who would not disclose the size of his firm’s stake in Pinterest.

And yet despite Mr. Silbermann’s approach — or maybe because of it — the company is worth $12.3 billion and growth is accelerating. In the past week, the company crossed a new milestone — 250 million monthly active users. Those users have pinned 175 billion items on 3 billion virtual pinboards. The company is on track to top $700 million in revenue this year, a 50 percent increase over last year, according to a person familiar with the company. There is wide speculation that it will go public next year.

If Pinterest continues its trajectory, it could change the narrative of what it takes to build a successful company in Silicon Valley, a meaningful feat at a time that the start-up world is seeking new templates for leaders. If it doesn’t, it’ll serve as another example of wasted potential, or worse, a cautionary tale.