Re: Does this mean though...
"That if blockchains are compute and network intensive that as more data is added it becomes uneconomical to continue to hold onto the data? Especially if the data is rapidly changing as well as increasing in size (I thought that was one of the limitations of bitcoin that it was of a finite size for the initial data that the blockchain revolves around?) Surely then if it's in a constant state of flux and increasing in size the overheads would become exponential?"
Pretty much, yes. The computing time required to record the transactions becomes more and more onerous. At the moment the people recording this information are rewarded with Bitcoins. Let's see what happens if that is no longer the case.
