You're confusing concepts and blockchain fundamentals. "Uncloneability" is the double-spending problem solved by proof-of-work/hashcash scheme. The 51% attack is not the problem, it's just a requirement for a PoW based blockchain to work. Just like how you have 1/3 honest node requirements in traditional BFT distributed database designs.
svennek|4 years ago
IMHO cloneablitiy IS the problem, PoW is just a (very, very unfortunate) solution to that. PoS (stake as in possession, not pledging) is IMHO inherently impossible, so PoW is all we got, now and for ever...