This following is a work in progress.
We can never take entirely for granted the absolute trustworthiness of what we read, see or hear from media of any kind. This is the case for information from traditional news organizations, blogs, online videos and every other form.
As noted previously, even the best journalists make factual mistakes, sometimes serious ones, and we don’t always see the corrections. When small errors are endemic, rational people learn to have a small element of doubt about every assertion not backed up by unassailable evidence.
More worrisome in some ways are errors of omission, where journalists fail to ask the hard but necessary questions of people in power. Stenography for the powers-that-be, and the unfortunate tendency of assigning apparently equal weight to opposing viewpoints when one is right and the other is wrong, are not adequate substitutes for actual journalism; you don’t need a quote from Hitler when you’re doing a story about the Holocaust. The reader/listener/viewer needs to keep an eye out for such behavior.