Farmville, Mafia Wars and Restaurant City are Internet-based games that can be played on sites like Facebook, where millions of people have signed up.
But click on the wrong places in these virtual worlds, and you could lose real money without ever knowing it.
CBS News Science and Technology Correspondent Daniel Sieberg reported where there's a popular online trend like these games, advertisers are sure to follow. But the legitimate ads aren't the problem -- it's the ones that promise a free trinket or virtual cash to be used in your game. And if you're tricked into clicking, they start draining your money.
With his mother's permission, 12-year-old Eli (whose last name was not to be disclosed), loves to dig around in his digital garden. He plants seeds, and is earning virtual money in the popular mini-game on Facebook called "Farmville."
Eli explained, "The object of the game is to become one of the best farmer. You can buy animals."
But what looked like a harmless waste of time for Eli turned into an insidious scam that racked up more than $50 in cell phone charges.
Amy Dunkin, Eli's mother said, "The things on my bill were a horoscope alert, a ringtone thing."
Sieberg explained how the scam works: Some third-party advertisers are preying on the rising popularity of mini-games on social networking sites like Facebook. Farmville is one of the most popular with more than 60 million registered users.
Caroline McCarthy, a staff writer at CNET said, "It's big business and there is a lot of money at stake."
Deceptive internet ads -- like an ad discovered by the blog "TechCrunch" -- offer Farmville currency just to fill out an IQ quiz. To get the results, users are asked to send their cell phone number and enter a code -- and the scam is complete.
Then a fee -- $10 a month or more -- starts appearing on their cell phone bill.
McCarthy said, "I would be wary of anything that offers you free surveys because the moment you put in personal info like your cell phone number or credit card number they are probably charging you."
Mark Pincus, chief executive officer of Zynga, the maker of Farmville says the ad approval process is being overhauled, adding: "We recognize it is our responsibility to ensure that offers which generate a bad user experience are not shown with any of our games."
For Eli and his mom, it's a tough lesson about the seedier side of the Internet.
Amy Dunkin said, "We tend to take it for granted that all their friends are doing it so maybe we don't monitor it as closely as we should. I'm certainly going to look over his shoulder a bit more when he uses the Internet."
Sieberg added that Amy Dunkin has said the charges were removed from her cell phone bill. But it's hard to know how many people have been affected by this scam, he said. Facebook and MySpace say they're also cracking down, according to Sieberg. If you're concerned, he said, do not provide your cell phone, e-mail address, or any personal banking information when clicking on one of these ads -- or don't click on them at all as tempting as they may be.