IT’S NO FUN to start your day with an e-mail from a friend, relaying a message you knew might be out there but tried your best to avoid.

“This is either a sick joke or I am utterly outraged,” the subject line reads.

Then: “What is this bullshit? Do I need to stop following your girlfriend on Twitter?”

But I don’t have a girlfriend. It had ended one month earlier. It was bad enough to be in a city she compelled me to move to, and it was hard to escape the feeling that I was now living on enemy territory. I hadn’t gotten around to telling all my friends about my new status, though, which is why my friend, who was following my ex, was so curious about her latest tweet.

And there it was, copied and pasted in the body of his email, in big, unmistakable typeface — evidence that the Internet was now enemy territory, too.

“Didn’t realize having sex [with someone new] would be so scary sober.”

DO PEOPLE SHARE information about their sex lives on Twitter? To some extent, yes. Everyone knows that sad, sensationalized song lyrics in a status update can generally be equated with love recently lost. It’s been well-documented that you can easily change your relationship status on Facebook; there’s always a flurry of activity surrounding that highly anticipated incident. People seem to refer to the fact that they are having sex, or aren’t having sex, in very tangential ways—a “so happy. !!!” status probably indicates that, yes, the sex isn’t bad right now, while Radiohead lyrics probably mean the opposite.

But I feel like I don’t generally come across the hard, crude details very often—people don’t seem to explicitly acknowledge the act. That’s what stunned me about the tweet as I sat there, half in a trance, half horrified, staring at my computer screen.

Yet there was still that glimmer of doubt in the back of my mind, in spite of the fact that I was hopping mad. Maybe, I wondered. Maybe that’s what people do. And if I’m going to use Twitter and Facebook like everybody else, maybe I have to accept that I might be the person publicly maligned every once in a while.

It’s just a little bit fun, I guess, to see angry, keyboard-driven fights happen in public. I think that’s why people flock to the Missed Connections section of Craigslist, and why the anonymous skewering in the comments section of some sites can often be more entertaining than the article being commented upon. But I, myself, had never been the victim of a public comment of that sort, one that seemed so very out of line and vindictive.

I had unfollowed her on Twitter, of course. Her blog post about how she was starting to date again several weeks after we had broken up was the last straw. She knew that I had unfollowed her, and so, as she later told me, she felt liberated to write anything she wanted, with the assumption that I’d never see it because it wouldn’t appear in my feed.

But things have their way of getting around. My cousin, who was following her, had seen the tweet, and you already know about my friend’s shock. The news about the tweet was, logically, likely to get back to me one way or another.

WHY DID SHE write it? My best guess is that it was a way for her to show the world that, yes, she’s doing just fine, and that her sex life is all well and good. I suppose I’m writing this piece about what happened, in part, so that people will react to it and hopefully emphathize, in one way or another, with my plight. In a way, we’re both practicing a form of exhibitionism, one that is universal and existed well before Twitter became a solid part of the Internet’s foundation.

And when our right to express ourselves in that way gets attacked—like when I told her, later that day, that I didn’t appreciate hearing about her newfound adventures in bed—we get angry. And she performed admirably in that role, firing off a string of volcanic tweets, each tinged with a hint of apology. “I feel like I just got slammed through no fault of my own. It’s my life. WE BROKE UP. Fuck. [So why do I feel so guilty?]” A couple minutes later: “Plus, he UNFOLLOWED me. How was I to know he would read it? And even so, WE BROKE UP. A month ago. I feel like I’m in a ‘Friends’ episode.”

Self-expression is a pretty important thing, so it makes sense that we can get defensive about our right to have it. But social media has given that right a jolt; we’ve never had the opportunity to share of ourselves in such a public way before. People are bound to test out this new form of expression and stretch it out as far as it can go, because you just never know what people might think of your latest post. The idea of sticky subjects like love and sex getting caught in the crosshairs in a sometimes-negative fashion shouldn’t necessarily render us surprised.

It’s easy for me to say that this particular tweet went too far. We dated for two years; of course I would have some sort of snap reaction. But I don’t think it matters whether I was personally invested in the situation or not. If I came across a tweet like that on my own, I’m confident I’d consider something like that to be off-limits and, in a sense, over the line.

In this case, I think, someone had tested out Twitter’s capabilities and had stretched them to the point of breakage. And hopefully, when and if that happens, that person can recognize their mistake. Yes, of course, we often want to be able to show others who we are, and it’s thrilling to do so without any visible filter getting in the way. But doing so is dangerous, and every once in a while, you can expect carnage.

AGAIN SHE PLAYED the role of apologist, sending a contrite text (“Thought I was more anonymous than I actually am”) and deleting the tweet. I’m on the fence about whether that last scrubbing of the virtual history books is part of that act of apology, but I’ll give her the benefit of the doubt. I realized, after all, that she wasn’t the devil.

But what’s better? Obtuse, thinly-veiled references to your sex life in your status updates, masked nicely by an emotional poem that you just read? Or concise, jarring references to the dirty things you do in the privacy your own home?

The answer lies somewhere in the middle. I don’t think it’s my job to give you advice on what you should write about yourself. But I do know that if you handle sex in these spaces with a reasonable attitude, you’ll probably do OK. You’ll save face, and you’ll communicate with others in a way that makes sense for everyone.

And you just might avoid a few jealous messages from your ex-boyfriend.