We've all seen the professionals get it wrong. Sometimes very wrong.
Furthermore, dedicated ammatuers who focus on a particular subject often have quicker and better coverage of news on that topic. Professional mass media news often over simplifies news, sometimes to the point of almost losing the story.
Then we've all seen the bias of professional news organizations. Freedom of the press is for whoever owns one. Look at how all mainstream mass media was completely silent about SOPA until the Internet forced the issue into the public eye. Then, the professional journalists all told whatever story their owners wanted us to hear.
I'm not saying that professional journalism is all bad. It's just not all good either. And the same for ammatuers. It is up to you to decide what news sources you trust. Some professionals have, and should rightfully so, not be given any trust.
We now have news channels that are more about info-tainment and the most fantastical splashy graphics than they are about real news. Closing down bureaus and getting rid of real investigative reporters because it is cheaper to just do talking heads? Then we also have professional news sources whose entire purpose is to promote a particular ideology. So maybe, increasingly, the only difference between the ammatuers and professionals is how big a budget they have? Now TV news anchors have to be fashion models. But in the past they had to be journalists who eventually earned the position of anchor. They weren't models, they just had to look okay.
So I find arguments about the goodness of professional news over news on the internet to be less than completely convincing.