[kpcyrd]

This is the correct threat of a 51% attack, although if the currency is unpopular enough, had little use and everybody stopped mining, you could theoretically fork from the genesis block and replace the whole chain as soon as your fork becomes longer than the original chain.

There is little to gain from attacking a system _that_ unpopular, but you could "take" everybody's coins in that scenario.

[therein]

That's beyond a 51% attack, though. You'd have to have much higher hash rate than that to catch up to the chaintip from scratch as you mine.

[oconnor663]

That's a good point, I never thought about it that way.