LinkedIn may be the world's leading professional social network, but that is also contributing to its potential value to hackers. Social networks have always attracted hackers. Sites like Facebook are regularly prone to a variety of different attacks, as members' willingness to share stuff quickly becomes there undoing. Before thinking about that hilarious picture of a singing cat that came from somebody they didn't know, they've clicked it and downloaded malware. As LinkedIn grows (150 million members and counting), the interest from hackers grows with it. Behavior on LinkedIn makes it a particularly useful target for hackers. On Facebook, users can be encouraged to keep their accounts private and secure and they tend to be wary about the people they share personal information with. On LinkedIn, a different set of rules exist by the very nature of the site. For a start, users potentially want to be sought out and contacted by recruiters and poten...