[W]hen Gail Devery's 9-year old daughter received a $29.95 membership in the Miley Cyrus Fan Club as a gift, Devery figured online access to the MileyWorld.com site that came with the membership would allow Dani to watch music videos of the Hannah Montana star or play games.

What she didn't know was that MileyWorld also features an interactive chat room, and there's no way to know who is lurking in there.

"I wasn't very happy about that. I told her I was going to limit what she would be allowed to do," said Devery, who lives in Bloomington. Her concern grew after she learned that when Dani registered as a member, she used her own name plus a five-digit number. "The first time I heard this voice say 'Hi, Dani' when she logged on, it really scared me," Devery said.

With fun names like MileyWorld, Club Penguin, Webkinz and Neopets, social networking sites specifically targeting elementary- and middle-school kids are exploding. According to online market research group eMarketer, about 8.2 million kids ages 3 to 17 already participate in virtual world activities and half of all kids who use the Web are expected to be part of online communities within four years.

For parents, this means greater fears about cyber-predators and more responsibility for teaching their young kids important online safety rules. "Parents really have to be vigilant about the sites they'll let their kids play on," said Perry Aftab, executive director of WiredSafety.org, a national online Internet safety and resource organization.

"Whenever you allow your child to be involved in an interactive site, there is someone on the other side," she said. "Parents need to remember that. Learn everything about the sites your kids want to go on and establish rules right from the start."

As much as Devery talks about online safety with her children -- including 13-year-old Matt, who recently started playing the online interactive game "Runescape" -- she knows they are still vulnerable. Devery believes Dani thought she was following the rules by simply adding numbers to her name to sign on to the Miley Cyrus site.

While most kids' social networking sites have sections for parents on safety and privacy, questionable content is often not far out of reach. A recent visit to a Neopets forum uncovered a thread devoted to the disappearance of British 4-year-old Madeleine McCann and this posting: "Killed by her parents and hidden, then dishonored by massive media hype and further lies."

Not exactly a romp around a virtual playground and probably not the posting of a second-grader.

In addition to sites tied to popular TV channels such as Nickelodeon and Disney (which recently purchased Club Penguin for $350 million), there are "fashion" sites such as Bratz.com, which is devoted to all things related to the lippy dolls. Aftab, who monitors countless websites for kids, said she is "very concerned" about the Bratz site and has contacted the legal department for MGA Entertainment, the site sponsor.

The Bratz registration page requires name, address, date of birth, passwords, phone number and e-mail. Users can also submit a friend's name, phone number and e-mail address -- though experts say parents should tell kids to never give out information about others on a social networking site.

"I don't think they are taking child safety as seriously as they should be," she said. "When I called, they weren't particularly cooperative or interested in my concern."

Aftab plans to continue pursuing the issue with the company.

By contrast, Webkinz only asks participants for their name, birthdate and state. Further, many sites that offer interactive opportunities for game playing don't allow kids to truly interact socially with one another, because drop-down messages from characters are prefabricated.

"To the credit of many of the popular sites, they are doing a lot of things to make the sites safe, like the canned chats they have on Webkinz," said Michael Callahan, president of NoodleNet, a Texas company that recently launched software designed to keep kids ages 3-11 on parent-approved sites.

"The big issue is what happens when kids leave a 'safe' site," he said. "For example, there are a lot of really young kids that know about Google. They could easily find a lot of things parents don't want them to see." Clicking on banner ads or "prize winner" popups can also lead kids into trouble.

Sites such as MySpace stipulate users must be at least 14 years old to participate, but are computer savvy kids -- especially those who have grown tired of elementary school social networking -- more likely to try to enter sites geared for teenagers and beyond?

"At this point, it's too early to know if kids will be drawn in that direction, but we can speculate that children who have had an earlier initiation to the Internet will likely be heavier users in the future," said Douglas Gentile, director of research for the National Institute on Media and the Family in Minneapolis.