What is the Fourth Estate?

What is the fourth estate? Is new media technology responsible for the decline in newspapers?
What does it mean "maybe the internet is already the cyberspace of the fourth estate"?

The Fourth Estate is the name given to the press and according to Edward Burke is the most important estate (the others being the courts, religion and parliament).

I think new media technology is responsible for the decline in newspapers because it makes news and information immediatley available and incredibly accessible for all people wherever they are. You can access it over the phone, internet, mp3...in fact almost any device.
this emphasizes the meaning of "maybe the internet is already the cyberspace of the fourth estate?" because, as newspapers were once the easiest way to know what was going on in the world, the internet is now an even easier, FREE way. Why buy a 35p newspaper when you can read the whole thing online for free and not have to deal with inky fingers and crumpled paper... :]