Blockstack, blockchain and the future


I know that it’s not really related to Blockstack but I’d like to hear your opinions on that.

Blockchains are an append-only technique and thus will grow but never shrink. Having this, Bitcoin’s (and every other) blockchain will be really big. And in even further future potentially limitless big.
So the lookup time (and every other measurement) has to get bigger and bigger (as the data get more and more).

  1. How does these things scale when the blockchain is that big?
  2. Is there a possibility to “forget” data without forgetting important data of history?
  3. How does a “bloated” blockchain could be cleaned up later?
  4. What do you think about having every piece of data saved forever (and thus data never fade)?
  5. What do you think about “pruning bitcoin nodes”?
  6. Is it possible to square Zooko’s triangle without using blockchains?