The Economist, however, seems to have found a compromise that might just work. Everything over 90 days is pay only. And so is the main contents page of the print edition.
Which means you can see a page from the most recent issue if someone links to it. And you can see a few major stories via the front page. But if you want to find your way to the rest of it - you'll need to pay for it. Which is just annoying enough that, if you're the kind of person who _wants_ to read The Economist on a regular basis you'll pay for it.
It strikes me as a good balance - nicely done.