This is an interesting perspective. The logical conclusion of this perspective is that the people who currently are paid to be reporters, editors, writers, photographers, etc. add little to no value to the world. Similarly, that news can exist without primary sources to exchange on Twitter of for bloggers to write about.
As a counterpoint, I'd suggest that:
1) Most people are not able to obsessively follow everyone on Twitter, and filter through the tweets for the most relevant news. For the first job of a news organ is to filter out the noise.
2) News aggregators must aggregate something. Take the homepage of HuffPo, for instance. Most of the articles posted there are written by people on the HuffPo payroll. Most of the others link to sites where someone was paid to write the article, like the Washington Post. None are direct links to a tweet.
3) Credibility is not an afterthought for most people. We expect our news outlets to at least make an attempt to be credible and/or publicize their biases.
4) Prominent bloggers don't typically interview local officials. Local officials matter, but they are not sexy and often must be visited in person for interviews. The general point here is that very few people will cover some important parts of the news for free, because doing it sucks.