privacy threats

[coderman]

if you had to rank each of the following in order from greatest to
least privacy invasion, how would you rank them?

- global eavesdroppers: NSA, etc.
- corporate aggregators: Acxiom, ChoicePoint, etc.
- social network sites and blogs: MySpace, LiveJournal, etc.

NSA is often a villain due to the shear breadth of data they monitor. 
But corporate privacy invaders can get a level of detail on your
person that even Big Brother envies.  and just how much personal
detail do people willingly broadcast to the world through social
networks and online journals (knowingly or unknowingly)?

how would you protect your privacy in each of these three contexts?