A good blog is conversational because it's porous, not just on the web, but of the web. The joy of writing one is that you don't have to explain everything, you can just link to it. If your reader wants to pursue that link she will, if she doesn't she can continue with you. The other great advantage is the way the possibility of feedback is built-in, and the real value often comes from the discussion in the comments, where your idea is really examined and refined. I suspect that's why most blog posts look so half-formed compared with print articles. They're not designed to be finished thoughts, they're offers of conversation, thought-starters, provocations. (Or at least that's what I tell myself every time I write a blog post that just dribbles to an inconclusive ending.)
All that combined with the fast pace of the blogosphere and the minimal cost of entry makes it a buzzy, messy, democratic place, where every good thought leads to a good conversation and every good conversation is global.
In contrast, print can often look stodgy, stale and slow, but despite that there's still something very compelling about it. And it's not just because this can be read on the loo. Partly it's because you always feel like you have to try and construct a decent argument here, make a point, explain something clearly and round it off with a snappy ending. We're not in a conversation, so I have some obligation to offer a complete idea. But the bigger difference is that the limitations of the format help provide its authority. There's only so much real estate available, magazines aren't cheap to make, or free to access, so editorial decisions have to be made; quality has to be determined, standards have to be set. Which means you don't get the meritocratic, but mediocre sprawl of so many online publications.
These characteristics are worth thinking about when planning brand communications; it's not about costs per thousand, it's about deciding whether you want to be discursive or authoritative, whether you want to start a conversation or make a case. And it's about realising that you should never promise a snappy ending if you haven't got one.