What? That's not true. You don't need more than one CPU miner online for tx to go through. That's why there are difficulty adjustments.

But as number of miners drop arent btc at risk of a 50% attack?

	▲	groundzeros2015 an hour ago \| parent [-]
		But if you have anywhere near the market power to do a 50% attack, you can make a lot of money mining.