But mining by and large is its own separate entity, not completely divorced from bitcoin world, but certainly operating at an arms length.
I'm not so certain. At the moment I think it has quite a strong influence on the current price though its influence will eventaully go by definition.
It then depends on how well BTC has been able to convince the mainstream to accept its prescence. Personally I think its a no-brainer for acceptance as long as it doesn't have too great a volatiity, can't be cracked and can't be manipulated too easily (though we're all quite happy to accept a currency which can be at the moment viz USD, GBP etc).
There are so many arguments in favour of BTC, it would be a shame to find it doesn't gain ground in the mainstream.
Everyone says that miners contribute 'such a small amount of btc' that it doesn't affect btc prices but I'm a miner - and I notice patterns. I tend to sell my btc (hey gotta pay electric bills!) on the third tues or wed of each month. That's the only time I sell... It's when I am able to the most (on average) for the entire month.
As asic tech becomes more available we are going to see the price crash - no sane miner is going to sit on BTC made in a short period of time when he can sell it and recoup it's purchase cost. Since difficulty is a reactive process... we'll see ~2 weeks of coins entering the wallets of miners in a shorter timeframe. This will have a negative effect on price. But only in the short term. Once the miner has 'ROI' he'll revert to only selling the coins he needs to pay electric and saving the rest... or spending them to buy goods and services in the bitcoin economy.
That being said: If miners have an effect on price... then I wouldn't expect it to vanish ever. This is what we mean when we talk about 'adoption' there must at some point be enough transaction fees to replace and exceed the block reward (it may not happen during this block reward, but I'd expect it at after the halving and before the next one). If this doesn't happen then bitcoin will fail. Miners secure the network and if the economic incentive to do so vanishes so will most of the miners - reducing the security of the network and eventually leading to the failure of bitcoin. I would expect it to grow over time as velocity increases and more and more transaction fees are packed into each block.
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As for adoption, I think we're in solid with the black market and organized crime... at this point all we need is porn to adopt it as a primary payment method and that will be all it takes. IMO grow the mainstream as much as we're able - but don't forget that porn should be the market we chase. It's been responsible for the so many technical advances and tends to carry them from 'geeky' to 'mainstream' in a very short time period.