Fact-checking politicians seems to be the journalistic "in" thing to do this campaign season. Aside from the self-aggrandizing nature of such pronouncements, there isn't anything necessarily wrong with the concept.
The devil is in the details, however. Over at the Wall Street Journal, James Taranto notes that these esoteric fact check stories too often end up as opinion pieces criticizing the policies or rhetoric of politicians.
In more cases than not, it's Republicans who bear the brunt of such "corrections," simply because truth in politics is often a highly subjective thing. Taranto focuses on one particular fact check by USA Today criticizing a John McCain ad for quoting Barack Obama out of context: