I don't think it's true at all. The media made just as many mistakes before the internet. The difference is there wasn't anybody to call them on it. Recall CBS tried to throw a presidential election with obviously forged documents, something they would have gotten away with a few decades earlier.
The media is not a monolith. Go read some history, and figure that a) people have been pulling stunts like that since the US was founded and b) they were typically exposed by competitors in the media.
Back in 1798, no less a person than George Washington was griping that the Democrats (under Thomas Jefferson - not to be confused with today's Democratic party) were a bunch of malcontents whose primary object was to overturn the government: http://www.pbs.org/georgewashington/collection/post_pres_179...
"The media made just as many mistakes before the internet. The difference is there wasn't anybody to call them on it."
The first part of this statement is tricky to validate. "The media" constitutes a much broader set these days, with lower barriers to qualification as part of that set. When you say that the media made "just as many mistakes," I suspect you're really trying to say that they "were equally susceptible to mistakes" -- lending weight to the second part of your statement, i.e., that Old Media were less accountable for any mistakes they made, simply because the Old Media were a smaller and more exclusive club, exercising proportionally greater control over the message.
I don't think your first statement is easily supported, or even theoretically supportable. But the second statement is interesting, and is worthy of some serious, in-depth study. Basically: we've got more people running around calling themselves journalists these days, and we've got all sorts of platforms that give the voice of the mob a lot more firing power. Is this a net- good thing or a net- bad thing w/r/t accountability? What about quality? Crowdsourcing can cut both ways, for good (scale, scale, scale) and for bad (variance, mob mindset, etc.).
We're trading the tyranny of the minority for the tyranny of the majority, and which tyrant is actually worse? I suspect the answer isn't as obvious as it may appear.
