The June 11th BMJ has an interesting letter suggesting journals should price articles for non-subscribers at $0.99 just like songs on iTunes.
The author, Nicholas Moore, points out that current prices ($10-$40/article where a yearly subscription is on the order of $80-$120) encourage illegal photocopying. At a reasonable price, many users would choose to download rather than be bothered to, say, go to the library. He correctly notes that total revenue to the journal would almost certainly increase (the one exception is if there are institutional users, say investment banks, who need offical copies and pay for them, but don’t subscribe to the journal, but that seems unlikely).
This might also be a good model for institutional licensing. Rather than a flat fee, institutions could pay by download.