Stay briefed with online networks

There are some threads/comments catching my attention about topics that maybe I would never notice just by reading the newspaper or watching TV. On some topics receive much more information, then just reading the newspaper or watching TV.
Can you rely on online network of friends to keep briefed on what is happening in the world ? Can you have an objective idea of the subject?
What about the so-called professional bloggers that are paid to input positive or negative information on certain topics? Do these type of bloggers really exist ?