Hi, thank you very much for your answers.

Part of my questions were piqued by this blog post (https://blog.ethereum.org/2015/08/07/on-public-and-private-b...) which defined a private blockchain as a "blockchain where write permissions are kept centralized to one organization". I think that it might be the case of people piggy backing on the buzzword and that people are using blockchain as a sort of computerized ledger.

So, generally speaking, a coin with a larger number of loyal miners will be more resilient than another with less loyal miners?

I think I made a mistake with the rising transaction costs - in USD they have risen with the price of BTC but have been rebased a few times.