I established a Facebook account in 2008. My motivation was ignoble: I wanted to distribute my journalism more widely. I have acquired since then just over four thousand “friends”—in Afghanistan, Pakistan, India, the Middle East, and of course, closer to home. I have discovered the appeal of Facebook’s community—for example, the extraordinary emotional support that swells in virtual space when people come together online around a friend’s illness or life celebrations.

Through its bedrock appeals to friendship, community, public identity, and activism—and its commercial exploitation of these values—Facebook is an unprecedented synthesis of corporate and public spaces. The corporation’s social contract with users is ambitious, yet neither its governance system nor its young ruler seem trustworthy. Then came this month’s initial public offering of stock—a chaotic and revealing event—which promises to put the whole enterprise under even greater pressure.

There are many reasons to be skeptical about Facebook’s I.P.O., which raised $16 billion for the company. For investors, as my colleague John Cassidy has pointed out, the company’s founders and early investors are likely to do better with this much-hyped event than individual investors. The offering itself was as visible a disaster as a lead underwriting bank (in this case, Morgan Stanley) has turned in for some time: Facebook shares have fallen by more than ten per cent; there were trading screwups by Nasdaq; and lawsuits and regulatory investigations into whether Morgan and Facebook properly shared information with investors have already started.

This launch-pad explosion is also one more reason to be wary of what my colleague James Surowiecki has analyzed: Facebook’s two-tiered corporate-governance system, which ensures that founder Mark Zuckerberg retains firm control, and can’t be easily challenged by dissident shareholders, even if he steers badly off course, as highly self-confident men in their late twenties sometimes do.

Those are reasons for investors to be doubtful; at least as worrying is what the I.P.O.-palooza signals about Facebook’s sovereignty over citizens, here and abroad. Facebook has become a public square of global importance. By the end of the summer, it may have more than a billion users, or about fifteen per cent of the world’s population. Some of these people are restive and see Facebook as a substitute public space for speech and dissent that their own authoritarian regimes don’t provide. Facebook users have already helped to foment revolution in some places (Egypt and Tunisia) and are still trying, at great cost, to overthrow one of the Middle East’s most brutal regimes.

Within the United States, Facebook is a venue for all sorts of issue and political campaigns. And yet, on the site, as a practical matter, what speech is permitted or banned is determined largely by Facebook’s terms of service. The terms function as a corporate constitution binding users to the provider’s conception of what speech is acceptable. My colleague at the New America Foundation, Rebecca MacKinnnon, in her recent book “Consent of the Networked,” calls this realm “Facebookistan.” Once Facebook users sign on and accept the terms of service, their postings are subordinate to the corporation’s rules, for as long as they choose to stay. In a place like Syria, the Facebook rules users encounter are much more permissive than local laws; in the United States, that is not so clear.

You might expect dense legalese, but the terms’ language is clear and soaring, echoing the tones of constitutional documents. Some of the declaratory sentences lay out the commitments by Facebook’s royal “We.” Others describe the obligations of the subject “You.” The terms are organized into sections, like articles. One entitled “Safety” seems to self-consciously echo the Ten Commandments: “You will not bully, intimidate, or harass any user…. You will not post content that: is hateful, threatening or pornographic; incites violence; or contains nudity or graphic or gratuitous violence.” And there is this hint of Facebook’s expansive authority: “You will not encourage or facilitate any violations of this Statement.”

The terms obfuscate Facebook’s business strategies in such simple language that the deception—the sense of what is being left out—is almost poetic: “Sometimes we get data from our advertising partners, customers, and other third parties that helps us (or them) deliver ads, understand online activity, and generally make Facebook better.”

Facebook has made jarring mistakes as its leaders have learned what it means to run a profit-motivated political and public forum. In 2009, for example, the corporation exposed Iranian dissidents to danger by unilaterally changing privacy rules that allowed the Iranian authorities to see the identities of activists’ online friends. The error was corrected quickly, but in general, Facebook has encouraged its users to accept greater and greater losses of privacy. Zuckerberg believes the world will be better off if it adopts “radical transparency,” as the journalist David Kirkpatrick put it in his book, “The Facebook Effect.”

Zuckerberg’s business model requires the trust and loyalty of his users so that he can make money from their participation, yet he must simultaneously stretch that trust by driving the site to maximize profits, including by selling users’ personal information. The I.P.O. last week will exacerbate this tension: Facebook’s huge valuation now puts pressure on the company’s strategists to increase its revenue-per-user. That means more ads, more data mining, and more creative thinking about new ways to commercialize the personal, cultural, political, and even revolutionary activity of users.

There is something vaguely dystopian about oppressed peoples in Syria or Iran seeking dignity and liberation inside a corporate sovereign that is, for its part, creating great wealth for its founders and asserting control over its users.

Facebook is hardly the only corporation managing these sorts of dilemmas—Google is a target of investigations seeking greater information about how it manages customer information it collects, about which it has sometimes been opaque, and it too has broken trust with users. Facebook points out that it has been responsive to revolts and protests from within. Zuckerberg proudly told Kirkpatrick that he revelled in the ways Facebook’s users had forced him to become more democratic: “History tells us that systems are most fairly governed when there is an open and transparent dialogue between the people who make decisions and those who are affected by them. We believe history will one day show that this principle holds true for companies as well.”

That is a laudable conception. Yet for now, at least, Facebook concedes to its users only when it judges that it is in the corporation’s interest to do so; what user votes and consultations there may be are purely advisory. As MacKinnon observes, this system suggests the political control strategies of the Chinese Communist Party: periodic campaigns of state-managed openness and managed local democracy.

While talking to varied audiences recently about my new book (warning: marketing ahead), “Private Empire: ExxonMobil and American Power,” I have been reminded how uneasy Americans from of all ideological orientations are about corporate power and sovereignty these days. They believe in capitalism and market efficiencies, to be sure, but they fear heavily concentrated private power, especially where it encroaches on their economic and personal choices. They ask, “What should we do?”

Perhaps it starts with exercising citizenship. I have decided to exercise mine—in Facebookistan, that is. This seems the right time to leave such a crowded and volatile public square.

It takes a while to find it, but if you are a Facebook user, there is a small settings button entitled “deactivate account.” If you click, Facebook displays the faces of people “who will miss you.” If you are determined nonetheless to depart, and scroll further down, you are required to choose a “reason for leaving” before you are permitted to go. Unfortunately, “inadequate citizen rule” or “doubts about corporate governance” are not among the choices. From the available list, I went with “I don’t feel safe on Facebook.”

Farewell, Facebook friends. May you enjoy everywhere the full rights of free citizens.

Illustration by Kate Prior.