I'm not sure upfront per-article micropayment is really that great. Comparing to traditional newspapers, the difference is that with the newspaper, you pay for a collection of articles, perhaps because you trust the paper to be interesting because of its reputation, perhaps because a headline caught your attention. Having paid, you also get added value from any number of articles you wouldn't have paid for on their own, and might not have even read if they were presented to you by themselves, for free. And yet you'd often find some of these articles the most interesting.

This doesn't happen if you're paying per article, based on a preview.