When can you sell news and information online?

You can’t profitably sell news or information online unless you can profitably sell it on paper, excluding advertising revenue.
Here’s how I think this works: once you charge for content online, your usage will be reduced to the point that selling online advertising become an impractical annoyance to your paying readers. So, you should be able to make money selling it on paper as well, if only as a newsletter.
The only exceptions I can think of might be sites that clearly add value from being online, such as speed, interactivity, or use of multimedia. I’m not aware of any sites that do this now.
I believe this rule also applies to the online editions of print publications. Only print pubs that could make money without advertising (probably in a much smaller format) can sell their news/info online. So, the WSJ can sell content online, but the San Francisco Chronicle cannot. Consumer Reports can sell content online, but Time cannot. Salon can’t profitably sell content online, because Atlantic and Harper’s can’t do it in print.