Selfies capture a moment in time—how we looked, where we were. Selfies say, "I was here." It started with celebrities, who took selfies as a way to show a different side of themselves. In the age of the paparazzi, selfies give celebs control over what they share. Then they made their way to youth, who are active on social media.

A Today/AOL study showed that for 65 percent of teenage girls, selfies boost self-confidence. It gives them control over how they present themselves online, at a time when they want more control than they're allowed. It's the idea that "I can't choose whether I go to school, what my curfew is, or when I can drive. But an outfit? That I can do."

The critics say, "Look at these girls who are so obsessed with their looks." That's taking away from their agency, from their feeling of comfort in their skin. It could also be a bit of envy that's motivating judgment. When someone takes a selfie looking great in a bikini, I chuckle to myself and think I might do the same thing if I looked that good.

Throwing around the term "narcissism," when you're not a mental health professional, might not be the best idea, since narcissism is mental health disorder. All social media, in some sense, is self-promoting. We're expressing ourselves in a way that we hope will get a response—that's what communication is.

There's so much negativity in this world. If this is an easy way to get a smile or a confidence boost, why wouldn't we do it? Would every phone have these resources if it wasn't something that was desired? Would "selfie" have been named the Oxford Dictionaries 2013 Word of the Year? I take "welfies" of myself and my daughter, and I post them because they make me happy. I hope that someday she'll look at them the same way I look at old photo albums of my parents.

But in this culture of likes and positivity, there is also the culture of trolls and criticism. In the case of the Alabama teenager who was criticized for tweeting a selfie at Auschwitz, it came down to context. If she had included, "Dad, I'm here on the anniversary of your death, thinking of how we studied World War II and wishing you were here with me"—but she was constrained by characters. Was it the best move? Maybe not. But we're judging a teenage girl on how she's processing grief in the loss of her father.

It's human nature to take a selfie and post it, because we see others do it. Even President Obama took a selfie in 2013 with the British and Danish prime ministers. We're staking our own American flag in whatever our moon is for that day.