[fanzhang]

It's still a good proxy for how easy it is to do. The attacker could buy hardware, rent from people not on nicehash, etc.

It's like how companies' market caps are determined by the the last few trades, even though the last few trades probably represent .01% (or less) of the shares in the company.

Probably best to read the numbers a bit qualitatively. A coin that is 2% nicehashable would require substantial efforts (probably negotiating with a few private pools) to mount an attack; perhaps impossible for a not-connected miner. Wheres coins approaching the double digit percents probably is quite possible if you have even lukewarm connections. And those near 100% or above are likely super vulnerable.

[xur17]

For smaller coins it's especially scary because existing miners could easily switch to the coin for a few hours to mount an attack.

[acchow]

There's already a GPU and ASIC shortage with prices skyrocketing - even without someone attempting a 51% attack. Being a PC gamer is tought right now - you often can't even find a GPU in stock!

Can't imagine how difficult it would be to hoard a ton of hardware.