Farmville, Mafia Wars, Restaurant City. All Internet games that can be played on sites like Facebook.

But click on the wrong places in these virtual worlds and players could lose real money without even knowing it. Some third-party advertisers are preying on the popularity of games on social networking sites.

Farmville has more than 60 million users. CNN reported in September that it may be the most widely played video game in existence. Deceptive Internet ads offer Farmville currency by just filling 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.

Users are advised to wary of anything that offers free surveys, because the moment personal information such as a phone number or credit card is provided, money is probably going to be taken. Some users have also reported receiving an onslaught of solicitors filling up their voicemails and e-mail accounts simply for clicking on an ad and starting to fill out information, even when the user stops filling out information and clicks out of the ad once its apparent the direction things are going.

The maker of Farmville says that the ad approval process is being overhauled. Facebook and MySpace say that they are also cracking down.

The good news is, players are getting these charges removed from their cell phone ads. For those concerned, do not provide personal information, even an e-mail address, when clicking on these ads.

Or better yet, don't click on them at all.