"Next time you blog or post an update to your social
networking site, consider what the net of all of your online postings
could reveal about what’s really going on inside your head.

Security researchers Nitesh Dhanjani and Akshay Aggarwal have
been researching how your online persona and activity can actually be
used to hack into your psyche for intelligence-gathering and even as a
way to influence your behavior. They’ll be presenting their work at
Microsoft’s upcoming Blue Hat security summit in October.

“This is the next generation of hacking: ‘I want to hack you, not
your app,’” says Dhanjani, who is a senior manager with Ernst &
Young."

  - DarkReading

The article above mentions a site called We Feel Fine project,
a data-collection engine that automatically searches the Web every ten
minutes for expressions of human feelings from blogs and social
networking sites. It then graphs the mood of the Net in color.  The wefeelfine applet is here embeded below.  They say it make take up to a minute to load so be patient. (If it never loads, then either your browser needs a java plugin or your firewall is blocking it.)   Hover your mouse.  Click the links at the bottom left.  There's really some interesting slices on the collective blog psyche here.