I'd experimented with embedding Javascript Bitcoin miners in my website as a means of monetization without ads. I see this as a more intuitive version of that which restricts the user based on usage (posting rate) instead of on viewership.
The issue I encountered was a miniscule rate of return on the JS-based mining. Do you think that if HashCash integrates with BitCoin for monetization/mining purposes, JS speed will be a limiting factor?