The problem is going to be the volume, and how long it takes the reader to figure out what is going on. You can look at a photo and quickly realize something is wrong. With this, you may need to read a few paragraphs or even start reading through what else the "author" has written. That is effectively a denial-of-service attack on human comprehension.
Consider the issue of fake reviews: sometimes fake reviews are really obvious. Sometimes they aren't. Often the best way to pick out the fakes is to analyze all of the other reviews the user has written. That is going to become harder.
For very technical topics, where the reader comes with a strong background knowledge in that topic, picking out the fake material isn't too difficult. I suspect for the hazier things where the writers are more or less stating opinions, like politics, it is going to be incredibly difficult (for a human reader) to separate the bots from real people.
Consider the issue of fake reviews: sometimes fake reviews are really obvious. Sometimes they aren't. Often the best way to pick out the fakes is to analyze all of the other reviews the user has written. That is going to become harder.
For very technical topics, where the reader comes with a strong background knowledge in that topic, picking out the fake material isn't too difficult. I suspect for the hazier things where the writers are more or less stating opinions, like politics, it is going to be incredibly difficult (for a human reader) to separate the bots from real people.