After the 2 Verge/XVG 51% attacks i’am very carefully when i read 51% attack. In the case of Verge i turned out that as much as 1% hashpower had been enough to perform that timestamp spook attack and that’s why i think the term 51% attack should be very carefully used.
I’am not familar with BTG at all. But checking their last 10 days network hashrate i can not see any increase coming from somewhere, the network hashrate looks normal. That doesn’t exclude a 51% attack of course.
What i wold like to see is actually proof it’s a 51% attack with indeed 51%+ Hashpower and not exposing some coding bug, Timestamp spoofing and/or something similar …
About the hashingpower to lease. For the BTC hashingpower it’s pure SHA256 hashing power that can not leased/sent elesewhere. For the Ethereum hashingpower it’s different of course and may hit wherever a bad actors would like to hit.
And i wouldn’t call Zcash a “smaller coin”, it has a decent network with 10+x times the BTG network.
But i agree that smaller coins/projects with very small networks are indeed in danger, but than again, an attacker wants to make money and small projects/coins aren’t a good target with less exchanges, less value, less demand, less volume … Once a project gains in value/price it network hashrate normally goes up as well and reverse of course, see Bitcoin Gold where the network went from 53 to 20 Mh/s.