Miners of bitcoin will soon face a halving of the reward for operating the most popular cryptocurrency, in a pivotal event that is a test of survival, industry commentators say."The block reward halving tends to 'shake-out' the weaker mining operations," Simon Peters, analyst for trading company eToro, told AFP. "Unfortunately for some, with the lower block reward received it no longer becomes profitable to mine bitcoin and the operation shuts down or gets acquired by a larger rival."