My concern is that in the long term you'll see more and more consolidation of mining power, because economic forces will tend to push things in that direction.

My concern is that in the long term you'll see more and more consolidation of mining power, because economic forces will tend to push things in that direction. (That's what the articles I linked to above are saying.) At some point, it might not take "collusion" to manipulate the currency because somebody will be able to do it unilaterally.