I do not observe manipulation by the large mining pools. However, many people reading this thread in hopes of receiving 10% bitcoin dividends on the holdings are not aware that of the tens of thousands of Bitcoin mining rigs operating, almost none of them are actual miners. They are rather hashers who do not maintain the blockchain, nor validate blocks, nor propagate transactions. Rather they are delegated Proof-of-Work tasks by the pool operator, who is the actual miner.

Look at the following pie chart from Blockchain.info . In the Unknown pie slice are private datacenters and ASIC manufacturers that are large enough to keep the 1% typical pool fee for themselves. Suppose there are four very large datacenters in there. Count the named pie slices and add say 4 for the private datacenters in Unknown and get 12.

Those 12 miners control Proof-of-Work Bitcoin mining.

I am not really alarmed at this situation. It is not one that Satoshi envisioned when considering how miners would operate, but pools flow naturally from the motivation of miners for steady income as opposed to luck. Hashers, those who actually operate ASIC rigs, are free to move from pool to pool as they see fit to balance this pie chart.

My point is that concentration of mining power by large holders in a Proof-of-Stake scheme could not conceivably be worse than this . . .