There was a lot of chatter around Vitalik's comments about "big scary nodes" during EthCC. The Ethereum Foundation says that data stored by archive nodes (and not by the others) is the full history of Ethereum states, which can be derived using data stored in other nodes anyway.
The total number of full nodes is essentially what matters for Ethereum, not its archive node count. Current numbers indicate the network consists of almost 12,000 full nodes. “A reasonable lower-bounded number of nodes required is debatable – essentially if one trusted party had and served all the history it would be fine, but we’d be relying on a centralised party not disappearing, which thankfully is not the case here,” concluded Harrysson. Archive nodes might not be considered strict requirements for Ethereum to operate securely, but as it turns out, they aren’t as rare as they seem, even despite their apparent lack of utility.