Topic: independent media
The 5th estate is this writer's term for the accountability and integrity tests that experienced blogging brings to the traditional 'free press' (but probably more accurately described as Big Media) known as the '4th estate', which in turn is defined by these other institutional power structures in Australia and most western countries:
3rd estate - Judiciary
2nd estate - Executive government
1st estate - Parliament
This was in Fairfax press on Jan 20-21st January 2007 and it's a good read.