LAS VEGAS, NEV. — Social networking sites like Facebook, MySpace and LinkedIn are fast emerging as some of the most fertile grounds for malicious software, identity thieves and online mischief-makers. And while some of the talks given here at the Black Hat hacker conference would probably make most people want to avoid social networking sites altogether, it turns out that staying off of these networks entirely may not be the safest option either. The biggest danger from social networking sites is that they are all tripping over themselves to embed powerful functionality that most subscribers will never use, said Shawn Moyer, chief information security officer at Agura Digital Security, a Web and network security firm. Speaking with Nathan Hamiel, senior consultant for Idea Information Security, Moyer co-presented a talk today called “Satan is on My Friends List,” in which he demonstrated a plethora of ways that user-created applications popular on