David Paul Morris/Bloomberg News

As much as it pains me to say this: privacy is on its deathbed. I came to this sad realization recently when a stranger began leaving comments on photos I had uploaded to Instagram, the iPhone photo-sharing app.

After several comments — all of which were nice — I began wondering who this person was. Now the catch here is that she had used only a first name on her Instagram profile. You would think a first name online is enough to conceal your identity.

Trust me, it’s not.

So I set out, innocently and curiously, to figure who she was.

I knew this person lived in San Francisco, from her own photos. At first I tried Google, but a first name and city were not enough to narrow it down. Then I went to her photos and looked for people whom she had responded to in the comments. Eventually I found a conversation with someone clearly her friend. I easily found that person’s full name, went to the person’s Facebook friend list and searched for my commenter’s first name.

There it was: a full name. With that, I searched Google and before I knew it, I had this person’s phone number, home address and place of employment.

Creepy, right? I even had a link to a running app that she uses that showed the path of her morning run. This took all of 10 minutes.

Nearly everyone has done something like this. Often, you don’t even need a first name to find someone. Google, after all, has a feature that allows people to search with an actual image. No words or names required.

A friend who works in technology recently told me I would never be able to figure out her age online. She had gone to great lengths to hide it. It took me exactly two minutes. How? I found a photo on Facebook from her birthday party two years earlier. In the photo, on the corner of a table, sat a birthday cake that said “Happy Birthday,” and two candles that said “24.”

“We used to have privacy through obscurity online, so even if people had that information out there, the steps that it would take to aggregate it all were too great,” said Elizabeth Stark, a lecturer in law at Stanford who teaches about privacy on the Internet. “Previously you could have searched every photo on the Internet for a photo of Nick Bilton until you eventually found one, but that would take a lifetime. Now, facial recognition software can return more images about someone instantly.”

So who is at fault for this lack of privacy protection? Most people are oblivious. The companies won’t stop collecting information. And the government is slow to protect consumer privacy.

The Federal Trade Commission, set up to protect consumers, didn’t act until late last month when it cited Facebook for “unfair and deceptive” practices. This is great, but it is more than six years and 800 million users after Facebook began.

Maneesha Mithal, the associate director of the Federal Trade Commission’s division of privacy and identity protection, acknowledged in a phone interview that technology had moved quicker than the government could act. The F.T.C.’s investigation of Facebook, she said, “has been a bit of a moving target.”

Ms. Stark of Stanford says she doesn’t believe that privacy is completely dead. She says people have learned from each privacy debacle. But the companies are not slowing down.

The tools that aggregate information are only getting smarter. The government isn’t getting faster. And Ms. Mithal said not much could be done about the damage already inflicted. “Our order only provides protection going forward,” she said. “The only real option to protect information going backwards would be to delete your Facebook account.”

Now which one of us is going to do that?