I always wondered about that and perhaps someone here can explain. After bitcoin reaches its "full" volume, mining rewards will go away and the only way miner income can stay the same is if transaction fees rise to match. Since the competition of miners basically converges to "block reward is equal to electricity cost equivalent", this would mean transaction costs increase to an insanely huge amount. Not paying the larger transaction costs would lead to the less efficient miners being squeezed out of the pool of miners, leading to less hashing power overall and thus an increased vulnerability to attack.
How does the system intend to keep up miner income after all bitcoins have been mined?
How does the system intend to keep up miner income after all bitcoins have been mined?