Bitcoin mining to earn money from free web content or mobile apps

Recently there have been discussions about how to pay content generators money for reading their content. E.g. How do I pay a good journalist who writes a great news blog for his or her work? Has anyone thought embedding Bitcoin mining JavaScript code that runs in the Browser while the reader is reading the content? Similar idea (native code instead of JavaScript) could be used to support free apps on mobile phones and tablets. This idea has several nice properties: 1. The content creator gets paid directly by mining Bitcoin. 2. The payoff is proportional to the amount of time the content or application is used by the user. 3. No need for ads to support content or free apps.

Unfortunately, the idea also has a couple of disadvantages that I can think of: 1. I have read that it gets progressively harder to mine Bitcoin. Depending on the exchange rate of Bitcoin to physical goods, this could be a problem. My guess is this is a flaw due to the design decisions of Bitcoin. Another virtual currency designed so that mining it does not get progressively less fruitful, would solve this problem. 2. The User could hook the javascript/Browser and possibly steal the mined Bitcoins. This could be mitigated by making it hard enough that the payoff would be too small. Also, for the mobile apps, the hooking and stealing should be a lot harder.

The whole idea seems obvious, so I wonder if anyone has already tried or done this?