Here's the thing...every American voter has an opinion about Hillary Clinton and they're split about 50-50. If you look at just about every other presidential candidate, between 1/4 and 1/3 of those polled will say "they don't know" or that they're "undecided." Do national voter attitudes mean much in terms of a candidate's primary chances in Iowa, Nevada or South Carolina? Probably not. But does a candidate like Rudy Giuliani, who's thought of positively at this point by a majority of Americans have an advantage over a candidate like Hillary Clinton in the general election? Possibly, assuming he cures himself of foot in mouth disease.
So why are Kit Seeyle and Karl Rove so obsessed with favs/unfavs when it's hardly news anymore that Americans are divided about whether they like Hillary Clinton or that Americans generally think positively about Rudy Guiliani?
Good question. My guess is it's more fun to speculate about these things then to do any real reporting on the candidates' policy proposals or factual, state poll based looks at the levels of support for individual candidates in the early primary states.