BitUndo – Double Spending as a service

Double spends are not currently "very viable", as indicated by the fact that they were not happening and accepting instant payment is the standard. This is objective reality, not something you can argue away. A different world being theoretically possible does not translate into it magically happening with no effort. You are making an effort to change our happy situation for your own profit, in other words, to make Bitcoin less useful over the long run to benefit yourself in the short run. I can't tell if you're motivated by greed or a particularly poorly thought out world view.

Also, why are you claiming this is somehow specific to unconfirmed transactions? Corrupt miners can also rewrite the block chain. If you get paid enough and have enough hash power, why not see if you can overtake the chain head? So don't claim it's somehow specific to unconfirmed transactions. It isn't.

Bitcoin fundamentally assumes that the majority of mining power is "honest", defined to mean following the rules laid down by Satoshi in the core software. You can see this by simply reading the white paper:

"The system is secure as long as honest nodes collectively control more CPU power than any cooperating group of attacker nodes."

(last sentence, first page)

You are attempting to bribe miners to become "dishonest" and "attack the network" in Satoshi's language. If enough people did what you suggest, the system's fundamental assumption would be invalidated and the entire network would break. If merely a small number of people do it, it just makes the system unreliable, untrustworthy and pushes people towards centralised fixes like payment processors that levy higher fees, trusted third parties that prevent double spending, secure hardware, etc. All things that increase Bitcoin's costs and reduce its competitiveness vs regular banking. Doing this doesn't help anyone or prove any point, it just adds sand into an otherwise useful system by increasing transaction costs.

tl;dr you are like a kid kicking down someone's sandcastle on a beach, then saying "they should have been guarding it better, anyone could have done what i did!".

Bitcoin is a system that is woefully misunderstood by many people. It is not a honey badger. It is at heart a system that takes a positive view on humanity. It's a system built on the assumption that the majority of players are honest and stick to the rules. In a world in which most people think long term and don't spend all their time trying to stab each other in the back, this works.

But is humanity really that way? Or does society require a small number of rulers keeping the ruled in line? Every day that Bitcoin works well, the answer shifts towards "no, decentralisation of power can work". And if BitUndo gathers significant hash power, the answer shifts more towards "yes, decentralised solutions can't work if they rely on an honest majority".

If you read the literature, distributed systems very commonly require some kind of honest majority, if only because the definition of "honest" needs to be set by something. There isn't really a way to make Bitcoin work in a world where most other players are colluding against you.

IMO it depends on the specific ecosystem, and there is no definitive answer for this question. Some systems bring out the worst in people, some don't. However, as bitcoin is a financial system, greed is a major force that it must contend with. As the value of BTC grows, the incentive for bad behavior will grow with the rewards. For that reason, I personally cannot imagine that bitcoin can continue indefinitely without some sort of regulation. I'd love to be wrong about that, however.

It remains to be seen if BitUndo can realize their goal under the current framework. It's quite possible that the costs coupled with the initially low success rate and the desire for miners to protect the value of their holdings might prevent it from ever gaining traction. However, their efforts highlight an attack vector and there may be ways to disincentivize their scheme early on.

Perhaps more importantly, this feature doesn't actually rely on miners being dishonest. There is no rewriting of the blockchain going on. All that is required is that miners are greedy. That is, when two conflicting transactions are in the mempool, it requires that miners prefer the transaction that comes with a higher fee.