Fees don't seem like a viable option. Coins are realistically in competition with real world payments, and at best would garner a couple % for fees (capped by the CC processing fees). However, since they are paid by sender and do not offer benefits that CC affords, I would venture that the fees should be more in line with fees for ACH (or equivalent systems), and thus, not that much.
Paypal transaction volume is ~ 2.2 billion tx annually (VISA is ~ 78 billion and all electronic tx is probably on the order of a trillion tx annually).
Still lets consider a 30 year goal of 40% the size of Paypal =~ 1 billion tx annually. That is ~ 20K transactions per block.
ACH fees are ~ $0.20 per tx. So 20K tx * $0.20 ea = $4,000 per block block reward. Still I doubt fees would need to be that high. At ~$0.05 (whatever that ends up being in BTC) per tx avg block reward would be ~$1000 which would support a network 5x as strong as the current one.
This is ridiculous. Paypal is worth about $50 billion. This is the discounted present value of collecting monopoly txn fees from money sent through paypal. You can currently buy a similar monopoly over bitcoin for $10 million. Let's do some back of the envelope calculations to show that D&T's suggestions are idiotic.
D&T proposes that the network will be 5x as strong as the current one, so that the cost of obtaining monopoly will increase to $50 million. However, the value of the monopoly will be about 40% of the value of paypal's with 20k txns per block. That is monopolization of the network will be worth $20 billion. Hmm. $20 billion dollar asset priced at $50 million. Sounds like a very good deal. The network would quickly get owned with such puny fees. The owner would jack up fees to paypal levels and become very rich indeed.
So what kind of fees would you need to protect bitcoin from getting owned. Well you need to get that $50 million up to $20 billion. D&T's figures are off by about a factor of four hundred. How much do the fees need to be 400*$0.05=$20 per txn. Wow! $20 per txn, great low cost payment system that would be.
Proof-of-stake is the only long-run viable solution. Stop joking around with this nonsense about txn fees coming to the rescue. It doesn't pass the laugh test.
You bring up a good point, but also consider:
- That as Bitcoin becomes larger and more stable in value, people will be willing to take smaller ROI's on their mining equipment investments, thus increasing the "monopoly buyout" of Bitcoin. Right now, the ROI is around 7 months for a BFL miner (for example). Judging that a good stock might be somewhere in the 15 P/E ratio (in other words, ROI would be roughly in 15 years if no earnings were reinvested into the company), you could expect size of the mining network to eventually reach around 26 x as much as it currently is.
- That the fact of immediate devaluation of Bitcoins due to a monopoly would likely mean no one would ever attempt it. What good would it be to own a monopoly over a transaction system that no one uses anymore? After all, right now, assuming one could buy a monopoly over Bitcoin for $10 million, they could gain a potential $250/block, or $36,000/day, or $13M/year. But if the price crashes, that monopoly does no good. It would be a terribad investment strategy.
- That it would also take a lot of time and coordination to pull off a majority share of mining. Time in which others may hear about the plan, and fight against it by buying and utilizing more mining hardware themselves.