Could two or more of these large pool operators ever take advantage of their position, for example, by secretly partnering to gain control over new block generation?

Is pool formation and consolidation an unavoidable consequence of the increase in block difficulty, as more miners opt for small, 100% certain rewards instead of large, highly unlikely ones?

Should the consolidation of pool operators be cause for concern? Could the largest pools ever find a way to impose higher transaction fees on the network?

Are we witnessing the creation of a new type of centralized or oligopolistic financial system?

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[1] https://blockchain.info/pools

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Edits: changed title so it better reflects what I intended to write; also, added and expanded several questions.