Why @Plasma Resolves Exit Safety Before it Personally Even Attempts to Solve Scale.
@Plasma has been built based on a barebones yet unpleasant premise: off-chain execution will ultimately break. Operators are able to go out-of-service, block transactions or deny information. Rather than attempting to avert such failures under every cost, Plasma uses the probability of failure as a normal state of affairs and constructs the guarantees on the principle of recovery, rather than continuity.
This is the reason why exit safety is first. Plasma does not transfer the computation to Ethereum, but final ownership. Users are still able to withdraw their funds unilaterally with cryptographic proofs regardless of whether the @Plasma chain stops functioning or functions maliciously. Exit games, challenge time and fraud evidence are not written in the fine print: they are the very basic enforcement mechanism of the system.
Scaling can only be done after this escape hatch has been defined. Constraining what can be executed in the system is a way of delivering throughput, rather than providing more freedom of execution. A reduced expressiveness and increased user responsibility processing of the program are accepted by plasma in exchange to a very limited but powerful guarantee: even when everything breaks down, the funds can still be retrieved on Ethereum.
