What do you mean "garbage-collecting the chain"? I've never heard anything referred to as that. Does it just mean: Define a minimum balance, and let miners reap dust? Can your garbage-collection proposal where most of the block chain is eliminated be compatible with side chains?
I have nothing useful on side-chains yet. It is in my todo queue.
By garbage collecting the chain I mean eliminating all of the historical transaction data, and distilling the information content down to the minimum that is required to operate the coin: The association between controllers and the summed outputs which they control. Currently, almost no one is mixing, and the chain is growing about 2.3 gb/year. If it were transacting actively and mixing was in heavy use, I can see Moore's law running out of runway long before Monero ceased to be important. Definitely in my lifetime.
Got it, thanks. I think I mentioned in my above post that perhaps much of this historical transaction data could be kept off chain .. in something similar to a trusted banking system that issues certificates based on its own Monero holdings. How this protocol could scale with microtransactions/high trading volume is something that is yet to become fully apparent to me .. as we don't currently have need for them. I would suppose those with far more time evaluating cryptocurrencies than me would have useful insight here. Perhaps it could be done on chain though, to remove bloat and still keep on-chain transactions?