That's 2200TB. Which is 37 of the best 2016 HDDs.
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Would it be outlandish to say that in 2016, using improved technology which exists today, a node will require less than $10000 [...] Is dust as really as big of a problem as people make it out to be?
Uh. Your 2200TB of storage would, using the most cost effective hardware currently available, cost
$130,992 today. No doubt this will improve substantially in a few years 2016... but "less than $10,000" sounds a bit ambitious (even relative to past storage scaling)... and you've not justified your random division by 20.
But hey, just take that and run with it— At $10,000-and-growing in hardware costs just to store the data needed to check the validity of blocks efficiently, costs that have no direct income generation, would Bitcoin be a decenteralized system? I don't believe that it would be. It would be a distributed system, yes, but one with some dozen of major players and large mining pools in complete control of the system, subject to easy influence by regulators and organized crime, and with everyone else is stuck with them.
That might be the eventual outcome of Bitcoin— just as it seems the eventual outcome of originally-asset-backed government promissory notes was to become today's current unbacked currencies. But even if it is inevitable I'd like to see that outcome forestalled: A Bitcoin who's only selling part is a different set of cronies-in-charge is not especially attractive to the systems of central banks, and not especially attractive compared to payment systems with lower hardware cost and faster confirmations.
Do we need the 0 value outputs? Will pruning exist in the next few years? Will the size of the block chain realistically grow fast enough to reach some of the numbers I've had fun with in this post?
We have pruning now now just no way for nodes to find sources for blocks in order to sync up if real full nodes become sparse, so there is as of yet no knob to delete the old history. It's not used at all now except for reorgs, syncing up new peers, and rescanning restored wallet backups. Validation is against the pruned data.
How long will 13 year old computers be able to run a full node?
You're not talking about excluding just old systems, you're talking about excluding everything that isn't a commercial-scale price-of-a-cheap-car capital investment in dedicated-to-bitcoin hardware-that-doesn't-even-exist-yet. Requiring reasonably modern, even reasonably high end conventional hardware, is probably not great for decentralization but probably doesn't preclude it, but I think that going beyond that does. Fortunately the same scaling laws your arguing will turn $130k into $10k will also grant the same capabilities inexpensive systems in suitable time. Maybe. And when it does we should make use of it. What we shouldn't do is set ourselves up so our only choice is to toss the decentralization that made the system worth having because we let it bloat faster than the technology could keep up with.