Danielle Smith, who lives in Missouri, posted a family portrait, featuring herself, her husband and their two children, on a few different social networking sites. Two weeks ago, a friend of Danielle’s was driving though Prague when he spotted the Smiths’ portrait in the window of a grocery store. The picture had been repurposed into an advertisement. The owner of the grocery store said that the picture was from the Internet, and that he’d assumed it was computer generated. When he learned that it was a real picture of a real family, he removed the billboard. The Smiths, as well as the photographer who took the portrait, hadn’t authorized any use of the picture. Next time Smith posts a picture on the Internet, she says she’ll lower the resolution or add an electronic watermark.

This curious incident serves as a reminder that once pictures or information have been posted to a social networking site, it is impossible to predict where they might end up or who might access them. If you are concerned about protecting your privacy when using social networking sites, you may be interested in our Facebook Identity Theft Protection Guide or our MySpace Identity Theft Protection Guide. Or, for information about services that can help safeguard your identity, see our identity theft protection reviews and comparison.