Probably harder than it sounds now. Last time I checked, miners run custom made ASIC rigs. It's no longer kids with cheap GPUs and ROIs north of 100%. The netwo

Probably harder than it sounds now. Last time I checked, miners run custom made ASIC rigs. It's no longer kids with cheap GPUs and ROIs north of 100%. The network is 20 Thash/s and growing. Getting up to 51% would take a major budget and sophisticated acquisitions and ops. While the USG could do it, it would likely cost way more than the cost of letting the bitcoin network live.