No, bloggers do not have to take positions. There is no law or principle that requires writers to say, no matter how much or how little expertise they have, "This is what should be done. This is the right thing to do." One could argue, perhaps, that taking no position is a position in itself, but then "no position," "I don't know what to do," and "I am not too sure" are positions all too rarely taken.
In the same way that everyone can give advice to friends without telling them what to do, bloggers and pundits (and commenters, for that matter) can observe and opine while leaving the positions and decisions to those actually carrying out the actions. "The credit belongs to the man who is actually in the arena," as Theodore Roosevelt said, because they are the ones who have to take positions, in order to make choices. The rest of us have the good fortune to avoid that burden. We do not need to force positions on ourselves.
Andrew Sprung finds Downie's argument "refreshing" but incomplete:
In a democracy ... all of us are arguably 'in the arena' to at least a limited degree -- in fact, each of us to the degree we choose. If you vote, you undertake to judge elected officials' actions -- though not every action individually, and not right away. That's the job of the elect(ed), as Downie points out. Moreover, our judgment on any given issue is -- and should be -- informed by our evolving judgment of our our elected leader's judgment.
I guess my view is a personal one. I regard this blog as a constant bur to figure things out. As an opinion writer, it seems to me a professional duty to tackle issues in real time the way politicians responsible for them have to. Otherwise you can lapse into vague commentary to save yourself any embarrassment or error. A columnist has a few days to figure things out. On some questions, I have a few minutes, or a few hours. At least, that's how I distinguish blogging from other forms of opinion writing. It happens now. And now never ends.
By all means, change your mind, as I do from time to time, as events and facts change and as perspectives shift. But also take a position - with caveats, sure, with conditions, fine. But take one.