I don't think it's all that hard to determine what sources to trust and which not. At the moment the much-reviled mainstream media uses actual journalistic standards -- the reports have sources for the information, where they can they identify the sources. Where they can't, they ID them as anonymous, but there's actually someone who served as a source and several editors who trust the reporter to have accurately reported and represented that source. There are usually two levels of editor who guide the writing and make sure of the sources. Large publications employ a fact checker who makes sure the names are spelled right and other factoids. Those standards developed slowly (compared to journalism of, say, the 1700s -- a kind of Fox news for journalism (heh, heh, heh -- OK, that shows my bias...). Which is all to say that, with some experience of comparing the reading of articles, magazines & newspapers over time, we come to know who we can trust and that standards are in place to back the information given. We may not agree with the slant or bias, but the facts are generally agreed upon.
In spite of standards and protocols being in place, the vast information output of the Internet is not at that stage yet. I can think of only a few Internet-only publications that meet those standards (and even then I'm not sure -- but let's say Slate, Wired and perhaps a few others). The rest is caveat emptor. Because they don't have the revenue, they can't afford the levels of experienced editing, fact checking etc.
So I tend to use these two information sources for very different things. The print world for news and analysis of events. The Internet world for crowd sourced type stuff: reviews of books, gizmoes, very fast reporting of events (but with the full knowledge I'm only seeing raw footage which may have its own bias and who's source I don't know if I can trust to be a representation of events). Still, very often dramatic, compelling and worth watching. Just not useful for considered analysis of events.
That may change with time but Internet reporting will require more money to support the infrastructure to ensure reliable information.
George