If belief was _all_ that mattered then QE would actually work, rather than just being a way of transferring wealth from the economy as a whole into the banks. QE would be causing massive inflation if the new money was actually being circulated in the economy, but instead it's being used to cancel bad debts, being lent back to the government, and to some extent is being hoarded by the wealthy elite. Belief has little to do with it in this case.
No, belief has everything to do with it. The problem is that the FED's belief does not take into account how their policies influence collective belief and how it influences their behaviour. It does not matter what the minority believes. It matters what MOST of the people believe. And sometimes that belief cannot be expressed in words. The shopkeeper raises his prices, because he subconsciously notices that more money is flowing throughout the economy. Little does he know that this money is coming from money printing and is not actual real wealth. But he believes it is wealth nonetheless and he doesn't even think to put this belief in words, but he decides to act on this subconscious belief anyways. Only in the future will this shopkeeper notice how erronous his belief was, but he might never even understand where his error lay or that he made an error at all.
The fact that A belief does not correspond with what is actually taking place and that these beliefs are unable to see the chain reaction caused by their actions does not negate the argument that people's actions are ultimately influenced by what they believe.
It may very well be the case that the benefits of competition outweigh the dangers of diluting the crypto wealth pool, that's why in my original post in this thread I started by saying competition is good. I'm not arguing the relative merits of specific coins, I don't know enough about all the alts to feel I can do that with any authority.
There was a thread a while back where someone was proposing an altcoin that was backed by bitcoin, conceptually it would exist within bitcoin, and contribute towards it's market cap. I think that was a scam, but it was an interesting idea, and it would be a way to have alts without causing the problems I have outlined.
I'm pedantic, I have a pathological need to define things in unreasonable detail. What I have said may have little importance unless crypto goes mainstream in a ridiculously big way

Yes, I do think that in THEORY we could inflate BTC to oblivion by forcing people to use more and more altcoins (but only through force). When an altcoin is forced on the people and a new altcoin is introduced consistently with short intervals, the people would notice consistent price inflation and confidence would indeed be shaken. Only under such a scenario do I foresee a collapse of the currencies without printing the traditional way. But in practice, only a few altcoins would be chosen by the market. They would cause only temporary price inflation, but their deflationary nature would soon takeover and we would have overall deflation for each of the succesful coins. The existence of succesful altcoins would indeed steal marketcap away from BTC, but this shouldn't be a problem, because while the added supply of a new currency has actual effects on people's beliefs, ultimately they would still believe that scarcity exists despite this. And THAT belief would lead ultimately that deflation overtakes price inflation with the result of overall deflation.
That's my 2 cents.
