Teens generally don't think twice about including their first names and photos on their personal online profiles, but most refrain from using full names or making their profiles fully public, a new survey finds.

The Pew Internet and American Life Project reported Wednesday that two-thirds of teens with profiles on blogs or social-networking sites have restricted access to their profiles in some fashion, such as by requiring passwords or making them available only to friends on an approved list.

The study comes amid growing concerns about online predators and other dangers on popular online hangouts like News Corp.'s (NWS) MySpace and Facebook, which encourage their youth-oriented visitors to expand their circles of friends through messaging tools and personal profile pages.

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Social-networking sites have responded by offering users more controls over how much they make public and warning them about revealing too much.

According to Pew, fewer than a third of teens with profiles use their last names, and a similar number include their e-mail addresses. Only 2 percent list their cell phone numbers.

But 79 percent have included photos of themselves, with girls more likely to do so. Eighty-two percent use their first names, and half identify their schools.

"Teens are manifesting the tension between wanting to keep themselves safe online and wanting to share themselves with their friends and potentially make new ones," said Amanda Lenhart, a senior research specialist at Pew. "Teens, particularly girls and younger teens, have gotten the message about protecting themselves on social networks, but the fun of these networks is the ability to share yourself with others on them."

Dashiell Feiler, a 16-year-old high school junior, said he keeps his profiles open, but uses at most his first name and last initial. He said people who find him tend to be friends anyway, but he left off his full name as a precaution.

"I just thought I didn't want anybody to figure out where I live," he said.

According to Pew, 45 percent of online teens do not have profiles at all, a figure that contradicts widespread perceptions that the nation's youths are continually on MySpace. Lenhart said younger teens, in particular, tend to stay away, some because they fail to meet a site's minimum age requirements.

Most of the teens with profiles say they use the sites to stay in touch with existing friends. Only half of teens with social-networking profiles say they use the sites to make new friends.

A third of teens online say they have been contacted by strangers, not necessarily through social-networking sites. Of those, 21 percent say they responded to learn more about that person, and 23 percent say they felt scared or uncomfortable by the encounter.

The telephone study of 935 American youths, ages 12 to 17, and their parents was conducted Oct. 23 to Nov. 19 and has a margin of sampling error of plus or minus 4 percentage points.