There are fortunately thousands of Ethereum full nodes, just as for Bitcoin. This is good because it provides decentralisation and trust in the network.
For some reasons, there are also Ethereum archive nodes, these store more states of information than full nodes, but do not provide more trust (just easier lookup of stuff). Apparently critics believed archive nodes are needed for maximum trust, but that is not the case.
The buzz was that there are only few (one, two or maybe three?) of these archive nodes and that it takes ages to sync them.
Check some BitMEX research and twitter remarks below to get the picture.
I’ve stated publicly several times that there probably are just 3 or 4 Ethereum “full nodes” (in a Bitcoin sense), including the ones maintained by Ethereum Foundation & Consensys. Apparently, I was wrong! There’s just 1 of such nodes maintained by others. https://t.co/ClCgOlAKht pic.twitter.com/57vVTNcRO6— Giacomo Zucco [I identify as 7 tall black women] (@giacomozucco) March 12, 2019
They want to be able to provide ex. all token transactions of an address which is only possible with the data from a full archived node afaik— Pascal Brun (@IAmPascalB) March 12, 2019