I would say however that in my personal opinion, price is a stronger motivator for difficulty increase than simply awareness, looked at individually. Just knowing about bitcoin doesn't really motivate most people stuck in a fiat currency system unable to imagine life any other way (most people aren't all that smart), and the minimal profit made per card per day from mining doesn't really inspire many people (Oh I make $15 a day from my triple radeon rig? so what?). But when price takes off both those who are already invested get gold rush fever, and those who hear about magical money making inventions and ridiculous profits for doing nothing want to jump on board
Well, of course when you factor in such elements as "human nature", you can draw a circumstantial relationship between price and difficulty. But let's not forget that the difficulty was raised several times before there were even any exchanges, and that movement was driven primarily by awareness. We've already seen the scenario you describe where the price of the BTC spikes, and since then we've seen the price progressively diminish, with no corresponding drop in difficulty. In fact, none of the difficulty forecasts I've seen has any difficulty decreases at all.
I think it would be more accurate to say that difficulty does not
follow price, but it is
affected by it.
Well that's a fair point. But as I said it's all a very complex mishmash. It is much more difficult for difficulty to decrease than increase. Once you have invested into bitcoin you are invested. If you are making $5 that's still $5 you are making. And the fact is that mining is still ridiculously profitable. Even after all the difficulty increases I see about 1000 USD profit per month off 5GHash in possibly the most electrically expensive area in the country. If I weren't electrically limited I'd be boosting the difficulty up myself. There's simply no reason to see difficulty drop right now. In fact if it weren't for the volatility of bitcoin scaring investors from plopping money into it, and the zero-sum aspect I think you'd see difficulty increasing far faster than it is now even without a price increase, at the current price.
But that still relies on price being the primary motivator, with awareness a subfactor. Difficulty remained relatively constant for the first year and a half or so because both awareness was low, and price was nonexistant. People added value to the coin without exchanges though, there was a thriving "over the counter" trade system created, and this combined with more awareness of the coin caused more people to get on board, raising difficulty.
Aside from the small (now minority) group of enthusiasts who mine bitcoin because they believe in it becoming an eminent player in the world currency, most people playing with mining and trading bitcoin are profit seekers, speculators, and other opportunists, who follow price. And most of the new players who become aware of bitcoin choose to join because of the pricing/profitability.
Basically you will never disentangle price and awareness, but short of a change in human nature as you put it, you will not see awareness be the primary factor in bitcoin mining being taken up. And that's why satoshi constructed it that way in my opinion. To take advantage of human nature.
All my opinion of course.
Do any of these projections take into account the capital outlays needed to create the extra Th/s of computing power and the effects on future difficulty increases? How long do you believe that 10% increases are sustainable?
Right now, we are hovering around 12.5Th/s. To increase this 10% would mean that 1.25Th/s of new computing power would need to come online over the 10-14 day period. That is over 4,150 5830 video cards assuming 300Mh/s per card. That is $600k (for the most cost effective video card) in video cards alone not to mention other outlays of capital. If miners are buying 6850s, 6870s, 6950s or 6970s, the net dollar amounts move much higher.
Also, if we have a 10% difficultly increase for this round, to get to another 10% increase would mean another 1.375Th/s would need to come online over the next 14 day period.
Unless there is a new technology to drive more Gh/s per $$, I would assume that this will not be a sustainable trend and that we will eventually see a tapering off of difficulty increases.
Also, with more difficulty means that smaller players will be moved from being profitable to unprofitable which will have a net decrease of the total hashing power of the network.
Thoughts?
Just to answer you with some of what I said before, mining is still very very profitable right now. It will have to become about half as profitable as it is today (or about twice as difficult/half the price) before I would find myself squeezed out of mining, and again, that is because I live in literally the most energy expensive area in the united states (its even more costly than many european nations). There is still room for a great deal of growth before people begin to see outlays as being untenable. But yes obviously there is some point in the future where difficulty and expenses meet and you cannot have organic growth at that point.