The Blockchain Bubble Will Pop, What Next?

If that describes you, go invest in a new blockchain tech. There aren't actually that many -- most of the ICOs of the last year were for stuff built on the Ethereum network. Sort through that a bit and you'll find companies building entirely new blockchains, some of them incorporating very good, forward looking ideas.

Blockchain is still very young. You haven't missed out on anything. Do some homework. Invest.

But nothing useful has been built on a blockchain!

Go make something. You're smart. In the best traditions of the software industry it's almost entirely FOSS. Absolutely nothing stopping you from building something useful. And there's lots of funding available for those that do.

Saying blockchain is worthless is like saying public key cryptography is worthless. Before e-commerce it was sort of a novelty (the need for security was always there, sure). Now it's ubiquitous, as is e-commerce. The latter would not be possible without the former.

Even if the development is / remains purely driven by greed, the introduction of new financial markets and new investment vehicles means it's here to stay. There is zero chance this genie is going back in the bottle. Every day there are announcements about uptake by the finance industry and by governments.

But that's a shallow view of the possibilities. How about tamper-proof voting for governments? Nearly fee-less remittances? Un-censorable communication? Completely transparent non-profits? Trust-less provenance / chain of custody?

Let's be real. Humans are terrible to each other. Being to able to fight greed and corruption with a little math -- in a trust-less, incorruptible, self-sustaining way -- is potentially history changing.

Name one.

A 51% attack can do two things: Enable "double-spend" attacks - where the hash rate majority will ignore a block which was previoulsy mined and had a "confirmed" transaction, and instead mine from an older block which didn't have that transaction - but instead place a transaction paying themselves the money back. Anyone accepting payments over Bitcoin should use their common sense as to how many confirmations they should wait depending on the amount of money being transmitted. A 51% attack might eventually be able to write a chain longer than the current one, but it will take some time - and there is the chance that if it fails, the miner will have wasted his electricity costs.

The other attack a 51% hash power can perform is denial-of-service. They can ignore blocks containing transactions they do not want to include in the chain, and as long as they continue to mine the longer chain, those transactions will not succeed.

51% attacks can not change the rules of Bitcoin (although there are many people who wrongly believe this to be the case). If you try to change the rules, the rest of the network will reject your blocks and ignore you.

> what would stop a government from running the majority of blockchain nodes and gain consensus majority?

The costs, primarily. In the case that one party did accumulate a majority of hashing power, the network participants can agree to change the hashing algorithm to one which runs on commodity hardware. That would be many billions of dollars of specialized hardware equipment going down the drain, and will only make the system stronger by encouraging individual participation. Monero did this successfully, and plans to do it each 6 months to deter attempts to game their proof-of-work.

:D

Those two things aren't mutually exclusive. Blockchain solved some very interesting technical problems, much like a lot of advanced math might do. But as you pointed out, the discourse is around whether or not blockchain solved any useful problems, not just interesting problems.

Like others, I have yet to be convinced of a use case for which blockchain is the best solution (other than cryptocurrencies).