In a famous New Yorker magazine cartoon, one pooch sitting at a keyboard turns to another and says, "On the Internet, nobody knows you're a dog." The point, of course, is that on the Internet you can pretend to be whoever you want to be.
Someone saying his is tall, young, and handsome could in fact be a short squat, balding octogenarian. People have felt that, in some way, the Internet provided enough anonymity to protect them.
But that attitude began to change several years ago. As the Internet grew in popularity and the tools and places for self-expression became more widely available and easier to use, many people went from wanting to be anonymous online to revealing a lot of personal information. The advent of blogs and social networking sites like MySpace and Facebook accelerated this phenomenon.
Young people in particular are using the Internet to share personal information about themselves. Many write blogs or have personal profiles on social networking sites where they share their thoughts on everything from their parents, teachers, and friends, to, in some cases, their illegal activities.
These days, more than a few police departments regularly visit networking sites looking for hints or statements that might help them solve crimes. For example, a police officer in Overland Park, Kan., working as a resource officer at a local school, estimates that he'd experienced about 40 incidents over a three-year period "in which he confronted a student or parent about online activities that may have been crime-related," according to a Dec. 1 article on eSchoolNews (www.eschoolnews.com).
Even more interesting is the fact that young people are aware that they are revealing too much. In a recent study by the Pew Internet and American Life Project, 79 percent of teens agreed that kids are not as careful as they should be about the information they give out online.
But teens aren't the only ones freely giving out information. Adults appear very willing to do so as well. In August, a blogger named Simon Owens conducted what he called a social experiment. He went to the "Casual Encounters" section on the popular classified-ad website Craigslist and posted several different ads. Each one assumed a different identity and sexual orientation.
Most ads received a lukewarm response. But the ads in which he posed as a woman looking for a male partner were inundated with replies. In many responses, people gave their real names, e-mail addresses, and telephone numbers. Some even included photos.
"If a really malicious person wanted to get on Craigslist and ruin a lot of people's lives, he easily could," Mr. Owens wrote on his blog. "I had so much personal information and so many pictures of so many people, that I could have posted their names and pictures alongside their messages online somewhere and have their most treasured secrets available to anyone who Google-searched their names."
Why do people reveal information online that they would never share otherwise? Amanda Lenhart, senior research specialist, at the Pew Internet and American Life Project, suggests that people do so because they lack context online.
"There are plenty of places in the real world where we give away personal information," she says "But we have a context for it – we're at a friend's party and we give someone our phone number for instance. We trust that our friend would invite people to his or her party that we might have a shared interest with. It's a safe place to share information.
"But we lack that context online. So there is a real tension – people are saying 'I want to know you. I want the world to know me.' But because it's not physical, people think they are safe to put anything online while searching for that connection."
Ms. Lenhart adds that people still believe that only the people they know will ever be interested in anything they write online. They doubt it will be read by people all around the world.
Posting personal information on the Internet can have long-term effects. Many employers conduct online searches for a job applicant's postings. An article on blogger.com noted that some employers do daily checks of items that their employees may have posted, particularly on company blogs or bulletin boards (http://help.blogger.com/bin/answer.py?answer=41978).
The best advice offered by privacy experts: Remember that anything you post online can be read by millions.