> One of the strengths that's getting overlooked here is that crowd-sourced news seems to be more reliable than news from any one source. Everyone is biased, but if enough people are talking about something the bias tends to cancel out.

The problem with this is that people only have time to check a limited number of sources. Furthermore, many orders of magnitude more sources means that there are many orders of sources that are dangerously wrong as well. Thus, if someone sees a number articles/tweets/posts/whatever from a variety of people espousing that the Texas church shooter was an antifa commie starting the revolution, they are much more likely to believe it.

On top this, with so many sources, people need methods of filtering, and, of course, one of our primary methods of filtering is to find communities/people we tend to agree with. Thus, the now cliche echo chambers are born. These communities are furthermore highly susceptible to manipulation (see the russian facebook ads).

Furthermore, this makes the system fairly easy to take advantage of. If a number of people that seem unrelated online engage in a coordinated effort to spread a particular message, they can do it with ease, since when you see the same message from multiple, seemingly unrelated sources, you're much more likely to believe it.

So while you're right that we used to rely on gossip and hearsay, simply amplifying the number of sources in no way implies that we're getting a less biased message.