> Why is the fact that arbitrage is harder with btc a disadvantage
Arbitrage is the method by which segregated markets are aggregated into a single market with a common price; if that is harder you have segregated markets.
> And the fact that the "price" reflects recent sales rather than future sales seems, well, obvious, and identical to other securities/commodities.
The same issue is raised with commodity/security markets in general, but it's practically more significant when the market(s) for a product have significant liquidity issues.
Arbitrage is the method by which segregated markets are aggregated into a single market with a common price; if that is harder you have segregated markets.
> And the fact that the "price" reflects recent sales rather than future sales seems, well, obvious, and identical to other securities/commodities.
The same issue is raised with commodity/security markets in general, but it's practically more significant when the market(s) for a product have significant liquidity issues.