According to this PCWorld article, social networking sites and iPhone Apps will be at the top of the list for malicious hacker targets in 2010.
This matches feelings throughout the security industry that social networking has become a large target for malicious hackers, already, and will continue throughout the new year. As always, verify what information you are sharing on social networking sites. Also, verify the identity of who you are allowing into your social network, make sure that Grandma really is Grandma. Be careful what applications these sites use. They may be malware.