Re: "systems where trust cannot be exploited"
That's a thought.
I was dabbling in Bitcoin in its early days but decided to bail out some time before things got wily (got something out of it, though--enough money for a new phone). You mention the idea of mining becoming centralized, and I agree that's an issue.
The issue that made me bail out of Bitcoin was the blockchain itself: essentially Bitcoin's ledger. Now, ask yourself. For any bank that has been around for a long, LONG time, where do they keep the official ledgers going back that long? That's the situation I'm starting to see with Bitcoin. You say anyone can obtain the blockchain.
That blockchain is currently approaching 65GB in size. In other words, it's a ledger the size of several libraries...and growing. This makes getting into Bitcoin in a serious way rather a PITA, especially for those with tight data caps. And the whole business seems to put you smack between Scylla and Charybdis. Keeping the blockchain decentralized is the only way to ensure its integrity, but it also means lots of people are going to have to keep copies of that huge blockchain. OTOH, trying to clip the chain into "volumes" has the potential to concentrate the number of sources of the complete blockchain much like how the miners are concentrated. This raises the potential for subverting or even usurping the blockchain.
The whole things seems to be rather like a huge, messed-up games without regulation because people don't trust the regulators.