Some years ago, I made the biggest mistake of my “media” career. No, not a crotch shot. But not good, either.

I was engaged in a pretty emotional back-and-forth with my former classmate and longtime friend Michael Kinsley, one of the most respected journalists in America. At the time, he was the editorial page editor of the Los Angeles Times, and along with some friends and students, I was waging a campaign of sorts to draw attention to the fact that women were woefully underrepresented on the opinion pages of newspapers — including my hometown paper, the L.A. Times.

In the exchange of e-mails, frustrated and exhausted, I wrote a sentence I never should have, which was interpreted as a personal attack based on health issues. I didn’t intend to be insensitive or cruel. God knows, I have suffered enough loss in my life. But I sent the e-mail and copied the women who were working with me. And then it went “viral” — a term I’m not even sure I understood at the time.

Kinsley was angry, and rightly so. His friends, among them columnists with wide audiences, went after me viciously. I tried to explain. I tried to apologize. To this day, I have tried sending messages through mutual friends expressing my regrets, to no avail.

I learned a valuable lesson. In the old days, you could make a mistake, apologize to the person involved and close the book. For better or worse, things went away.

A few months ago, my daughter was writing a piece for the Harvard Crimson about growing up in a family where rape (of me) was simply a fact of life. I told her about the first story that ever appeared in print about my experience — in the Harvard Crimson no less. She spent the better part of the day in the archives looking for it, but it was before the Internet, and it simply doesn’t exist anymore.

Life is different these days. If you don’t think before you hit the “send” button or the “post” tab, there is no undoing of the damage. Everything is findable.

Rep. Anthony Weiner has a lot of explaining to do to his beautiful and talented wife, who may well decide she doesn’t want to listen. But what should be a personal matter between a husband and a wife is instead an international sensation.

Did he really think he could post a crotch shot on the Internet and the world wouldn’t know? Apparently he did. And he is not the only one.

I can’t begin to count the number of times I have told young (and not so young) people that what they post on Facebook or send out on Twitter is part of their school or job application, that employers and admissions officers pay attention to these things, that if you don’t want your boss seeing you smoking pot, you shouldn’t post a picture of a bong on your Facebook page. And I can’t begin to count the number of times they ignore me and then can’t understand why they didn’t get the job or the school.

The Internet has brought us access and information we never had. It has allowed us to make connections that once would have been impossible. It has turned the world into a much smaller neighborhood than I ever could have imagined.

It also has turned expectations of privacy on their heads and mistakes into scandals that may be forgotten, but never will be lost. I am still sorry for my mistake, and I expect that Weiner will be sorry about his for the rest of his life.

— Best-selling author Susan Estrich is the Robert Kingsley Professor of Law and Political Science at the USC Law Center and was campaign manager for 1988 Democratic presidential nominee Michael Dukakis. Click here to contact her.