Towards the end of his often revelatory book, The Facebook Effect, David Kirkpatrick quotes company founder and chief executive Mark Zuckerberg on what he really wants out of business: "My goal was never to just create a company. A lot of people misinterpret that, as if I don't care about revenue or profit or any of those things. But what not being just a company means to me is not being just that – building something that actually makes a really big change in the world." It's a carefully enunciated view that takes into account two conflicting pressures on the Silicon Valley business: the desire to do something significant, and the imperative to make money.

At the end of his first full week as boss of a listed company, Mr Zuckerberg might well feel that he has accomplished one of those goals rather more successfully than the other. The story since Facebook shares were floated on the Nasdaq last Friday is a simple one: a brief surge in the price, followed by a sharp and severe plunge from which the stock has yet to recover. That has led to recriminations all round: at Nasdaq for apparently bungling the technicalities of the float; at the underwriter-in-chief, Morgan Stanley, for more fundamental errors; and of course at Facebook itself. There have been accusations that the flotation is another example of how Wall Street financiers rip off Main Street investors (who, if they bought on debut, are now heavily in the red), that the Facebook flop represents the bursting of another bubble, and that the model for the company is itself fatally flawed.

So far, so predictable. Whenever an investment falls seriously foul of its purchasers' expectations, anger and even lawsuits are never far behind. And when an investment comes good, the fury is normally forgotten. As one big-money investor observed, Amazon flopped on its listing on 17 May 1997 – and remained below its issue price for nearly two months. It's a safe bet that Jeff Bezos doesn't lose too much sleep over that now.

To return to Mr Zuckerberg's summary of his competing objectives, it's safe to say that Facebook has made "a really big change in the world". It is one of those companies that has made the transition from noun to verb: just as one Googles something or tweets about a news story, so you Facebook an acquaintance. The website has over 900 million subscribers, and takes up 14% of all the time Americans spend online. It has become one of the main channels by which people browse the news, or watch videos of piano-playing cats. These are extraordinary achievements for any company, let alone for one that has only been around for eight years.

And yet it is very hard to see how this adds up to a business that can be valued at 60 times its earnings on the stock market. Even Google trades at around 15 times its earnings. And there are giant obstacles to its growth as a business. First, it will struggle to turn its online advertising into a really convincing business: just last week, General Motors announced it was dropping its Facebook ads and said they weren't working. Coming from one of the biggest advertisers in the world, this is a major vote of no confidence in the medium. How Facebook makes advertising work on the smaller screens of smartphones is a big question that, the company itself admits, has yet to be satisfactorily answered. Then there is the issue of expansion: by rights, Mr Zuckerberg's business should be pushing into China and India and Brazil, but each of those countries has its own social-media favourites firmly in place. But one of the lessons of Silicon Valley is that even the biggest risks can come off – thanks to factors previously unthought of. Amazon's transition from bookseller to book publisher is a case in point. Mr Zuckerberg might just show he has the ingenuity to surprise cynics – and even if he doesn't, his attempts will be worth watching.