Gregory's Server
I think the charitable argument is that the many:many architecture of the Fediverse doesn't work for BIG networks due to hosting costs and fragility (the "can't see all the comments" problem), and this necessitates a few:many approach with caching layers (relays, AppViews).
They hope to make hosting "Google" cheap enough that it's plausible for a donation-funded org or small business to do it.
As @hazelweakly has noted, just hosting Hachyderm is $1k a month on owned servers.
@cwebber @Claire
I think the risk they're running with this approach is that there's no fundamental guarantee that the cost of being Google won't run into the tens of millions eventually, and as they're taking VC funding the incentives to avoid this may not be in place.
Fediverse spreads this cost around the network pretty "fairly" if less efficiently, hence the $12k / yr expense of hosting Hachyderm.