[1]: https://www.reddit.com/r/btc/comments/49osb4/examples_of_rbi...
[2]: https://medium.com/@octskyward/the-resolution-of-the-bitcoin...
[1]: https://www.reddit.com/r/btc/comments/49osb4/examples_of_rbi...
[2]: https://medium.com/@octskyward/the-resolution-of-the-bitcoin...
On the other hand a global payment system would require a currency which is at the very least stable (and not increasing in value). But a stable value might not be enough to cover the expenses of most of the miners. Mining is already dominated by Chinese miners which happen to have access to the cheapest electricity - which incidentally completely undermines the aspect of decentralization.
In summary it seems that at this point a decentralized payment system just appears to be too expensive (computationally) to be any serious competition for currencies in countries with a well established, trusted payment system. It still might be of use in the developing world.
It works in the other direction too. Lowered value lowers mining competition which LOWERS difficulty. It stabilizes itself automatically.