Although the Washington Post's Erik Wemple does state that overworked and undersourced journalists everywhere seem to be acting more as aggregators these days, it's Fox News (and their imitators) that seem to rely more on the same people that they attack to fill their space--and their viewers are too stupid to notice:
And when contacted, I assume that Irene Briganti was the Fox News PR person who said some sort of word salad that the Post relies on Media Matters.