That is like saying that there are no back doors in open source software because anyone can have a look at the source.
'The market' is a handful of powerful miners anyway. As if your 1 vote could do anything about some fork abandonment or whatever. Also, do you monitor the whole network constantly? You have to sleep at some point. You know who does constantly monitor the flow of currency to a somewhat trustworthy degree? Banks and governments do.
First of all, you seem to be addressing bitcoin in isolation and not crypto in general. What forces do you think make Bitcoin worth more than ETH or more than Bitcoin Cash? Market forces. Supply and demand. Just like all commodities. These are invisible hand forces that no single person controls at this point. Even if there are varying levels of centralization in the chains themselves, the market decides whether to back ETH or ETC or some mix of both. So, like any decentralized system, the network is monitored in a decentralized manner. The chains themselves have solved for consensus problems. That's the whole thing keeping blockchains going. No, banks don't constantly monitor everything (although admittedly, it's more than ever thanks to technology). Large amounts of cash still flow around the globe. And whether your government is trustworthy depends largely on which of the 195 nations you live in.
The worth of a cryptocurrency is a bit of a weird thing to me since the decision where the decimal point is arbitrary, the different cryptocurrencies aren't that different in value, they just use different decimal points. If ETH decided to shift the decimal point by two digits, it would suddenly be twice as much "worth" as bitcoin.
If a company issued twice as much stock, would it have a market cap that's twice as high as it's 1x issuance? If Amazon offers 100 AWS-Bux for every euro/yen/dollar would they bring in 10x as much revenue if they offered 1000 AWS-Bux for every euro/yen/dollar[1]? No, to suggest otherwise would be economic delusion; economic literacy doesn't seem to be the ETH's community's forte.
The quantity is irrelevant, the exchange rate that reaches equilibrium is what is relevant
[1] There are marginal second order effects with human psychology (people feeling like they got more of something)/ brokerage arrangements (1 share being the smallest divisible portion of ownership that a SE will clear causing share subdivisions needed to be cleared by a broker)
Companies issue more stock all the time and it definitely has some impact on the market as it devalues a single share.
If a company simply turned each share into two shares, then the market cap would be the same but the fractions of the markteshare that can be traded are smaller.
If the company suddenly issued the entire stock on the market again, the price would plummet to half.
You don't have to monitor constantly, just some time after you make a transaction. Long chain reversals grow exponentially unlikely the longer the chain gets.
In practice, this does not seem like a large problem.
