I'll also admit ignorance here, but it doesn't seem valid to compare overhead as percent of transaction vs overhead as percent of market cap. Current estimated

I'll also admit ignorance here, but it doesn't seem valid to compare overhead as percent of transaction vs overhead as percent of market cap. Current estimated USD Transaction Volume is ~$70 Million per day[1], so the transaction fees needed to sustain the $150k per day electricity overhead would be ~0.2%. All of the parameters in this calculation are in high flux of course (and we're not including total cost to mine here, just electricity), but when I've run this same calculation in the past at various times I've gotten similar results. Note also that mining is profitable enough due to new coin creation that transaction fees in practice are much smaller than this for now (average ~0.01%), but coin creation will gradually taper off over the years. 1] http://blockchain.info/charts/estimated-transaction-volume-usd?daysAverageString=7 http://blockchain.info/charts/estimated-transaction-volume-u...