In a way, there is already a system like this in your brain. Reputation is something you formulate yourself based on meta-information about the outlet you're reading. You do this already: ever read an article and look up at the URL to check and see if it's hosted at a reputable source, like nytimes.com or salon.com?

What would help is more meta data available to the reader. So, instead of measuring an unmeasurable "truthiness" (because really, what is truth, in the philosophical sense...) how about a Chrome plug-in that pulls down meta data from other sites that have written about this outlet.

So, you read NYTimes, and your little plug-i pops up some links to http://en.wikipedia.org/wiki/Jayson_Blair or some such similar thing. You can read up on that and see that there have been issue sin the past, but for the most part, NYTimes remains reputable.

I guess it would need some sort of Hacker News-like inaccuracy tracker. Post bad stories, more up-votes, more likely to be detected as relevant meta info on the TLD it comes from.