The one money matter that most Internet millionaires talk about openly is what start-ups they are investing in next. Expect many more such investments from Facebook executives. Indeed, that might be where the biggest chunk of their new wealth will go.

Off the corporate campuses and out of public view, it seems, there is little anxiety about spending. Friends of Facebook employees say that they have talked about buying houses, of course, but also planes — a seaplane even — and works by popular artists like Banksy, whose pieces can sell for hundreds of thousands of dollars. Just do not expect them to post about any of that on their Facebook pages.

To understand the contradictions of moneymaking in the Valley, it is instructive to look at another landmark public offering: Google in the summer of 2004. Just before it went public, a senior manager holding a baseball bat lectured a roomful of Google employees: Anyone who dared show up to work in a flashy sports car would soon find its windows shattered. The story is part of Valley lore. But it is also well known that the company’s three top executives have a collection of eight private jets, parked in a NASA hangar…

Mark Zuckerberg, Facebook’s chief executive, sets the tone at the company with his trademark rumpled hoodies that display no obvious brand name. He spent $7 million on a large but nondescript home in Palo Alto, a suburb so expensive that even a small, no-frills house easily goes for $1.5 million these days.