Last Friday, as his brainchild company went public, Mark Zuckerberg’s face filled the multistory video screen adorning the Times Square Reuters building, his image a grinning, pasty vision of triumph—little brother as Big Brother.

In the 30 seconds after the bell rang at the NASDAQ exchange, more than 80 million shares were traded, and with the IPO (really the night before, when the underwriting banks bought the stock from Facebook), Mr. Zuckerberg made $25 B.

But he wasn’t making any money off me.

I joined Facebook in 2007, back when you still had to identify your school to become a member. Carefully curated pics were promptly uploaded to my profile, and soon I was scrutinizing my future college classmates, accepting friend requests with bright-eyed, bushy-tailed pride. I was never really addicted to Facebook, but for several years I would log-on at least once daily, friend-ing old summer camp acquaintances and lustfully stalking sweet Laxers (look it up).

After a while, however, I found posting and viewing Spring break beach shots (cellulite airbrushed out, cleavage brushed in) vaguely vulgar. The entire site seemed to be based around a strange, self-branding tango of exhibitionism and voyeurism. Still, I maintained my account to keep in touch with friends, to make sure my little sister didn’t post any photos she would live to regret, and to participate in the enduring who-looked-hot/not dialogue with my peers.

Initially, I was even excited by the sharp-shot targeted ads. “Ee-gadz! I do want to check out that conflict-free diamond tennis bracelet, I do want to support Prop 19 and I do want to invest in blue-light acne treatment!” I found myself cooing over and over again. But after a while, Facebook’s apparent telepathy had me jittery. I was a 20-something, prep-school educated Californian with a hazily expressed penchant for all things acceptably unorthodox, and Mark Zuckerberg and his army of youthful-genius programmers had successfully pigeonholed me. I found myself fitting perfectly into the Facebook algorithm (or rather, it fitting perfectly into me), and no number of Grateful Dead dancing bear T-shirts could counterbalance it.

My attitude toward the site had already generally soured when I heard last February that Facebook was going public, but within a week of the news, I deactivated, permanently, and I’ll tell you why.

Aside from Facebook’s use of my clicking habits and social network connections to tailor ads, I had another unsettling realization. Facebook is a service and a product to its users. But they pay nothing to use it, and there is no native revenue stream. The value of the company—its main asset, to itself any and potential business partners—is the users themselves, and access to them and their information. What they were planning to sell shares of was me. It was you.