Yglesias puts his finger on one variety of professional insecurity:
Convention dictates that if I sit at a desk and read a transcript of what the press secretary said and then write about the transcript, I’m a lowly cheeto-eater. But if I sit in the White House press room and transcribe what the press secretary said, and then write about the transcript then that’s journalism. Similarly, if I travel around with the president and then read the pool reports that my colleagues write and then write about that: Journalism. But if I read the newspaper account of where the president went and then write about that: Cheetos.
One reason, however, that I blog rather than do cable is that I think I can get at more nuanced, detailed and factual truths online than on TV. I'm as parasitic as they are, but less geared toward pure entertainment - with more links and access to immediate information.