From John Dickerson in Slate:

Her abettors in this speculation are the Democratic National Committee and the media. The DNC wants Palin to be the face of the Republican future because Democrats think she’s a clown. The media has an interest in portraying Palin as a viable political candidate because that justifies endless coverage. She’d still be worth covering if she were just a political personality, but at some point the coverage would wane. Considering her as a serious contender gives a pretext for more coverage—which is good for ratings. Just ask Oprah: Her show with Palin was Oprah’s highest-rated since 2007, when 100 members of the Osmond family appeared. (For numerologists, that’s 1 Palin = 100 Osmonds.)

From Frank Rich in The New York Times:

Palin is far and away the most important brand in American politics after Barack Obama, and attention must be paid. Those who wishfully think her 15 minutes are up are deluding themselves.