Greg Sargent has a good write-up on Sam Stein's question at last night's prime-time Presidential press conference. Noting the real innovation behind The Huffington Post reporter's turn in the spotlight had more to do with what the outlets are doing online than the ideology of their reporters:

Some at the traditional news orgs are likely to see this decision as proof that the White House is determined to make use of an evolving Web-based apparatus of lefty news orgs that's supposedly more committed to advancing a partisan agenda than to doing balanced journalism. Whatever the White House's motives, the point is that some traditional journalists are likely to see the decision through the prism of their own presumed journalistic superiority.

But the real innovation isn't in what Obama did. It's in what outlets like HuffPo are doing. Places like HuffPo and my alma mater, Talking Points Memo, are striving to demonstrate that it needn't necessarily be mutually exclusive to care along with your audience what happens in politics -- to have a predisposition towards one outcome or another -- while simultaneously doing real journalism. This innovation isn't wholly confined to the left, though even some conservatives admit that it's more advanced on the liberal side.

Stein writes for an outlet whose predispositions are well known, but he produces fair, even-handed, thoroughly reported pieces. In other words, he's a legit reporter. And so ultimately it's perfectly natural that Obama took his question.