the shift of phishing attacks to social networks is particularly driven by the attempt to obtain user credentials
This shouldn't come as a surprise to anyone. As the guy from the privacy presentation (Rambana(?)) at securitytube pointed out, we are freely giving away all of our privacy. It's now trivially easy to post some shortened URL to twitter or myface, linking to a site hosting malware and collect all the info you want. As the HBGary hack points out, nearly everyone reuses passwords (including those that should know better...myself included) & usually only slightly alters them for online banking.
You might as well be posting a sign on your door saying
"A sucker lives here: feel free to break in and steal all my stuff because I'm too busy informing the world of all the trivial details of my boring life in order to feel less insignificant!" Oh wait, that's what people really are doing when they post stuff about them going out of town or elsewhere. The burglars thank you for your vanity.
Jonny, you may want to look into DeepFreeze or the free alternative BufferZone or my favorite, Sandboxie. It's not perfect protection but it'll help most people.