Server side rendering would exploit the fact that all of your clients are using the same resources to render the game - so you only need to keep 1 instance of mesh x in memory and you can render it for all clients.
As I said below if you have shared instance worlds like MMO you can do much more sharing, you can have shared effects just like you have a shared simulation for clients - the effects can then be optimized for techniques that might not be viable on consumer hardware - for eg. you might have some sort of world space global illumination technique - like radiance transfer. These techniques aren't usually used because you need a lot of memory + processing power - but you can get server GPUs with >10 GB of memory and more in the future you could have one dedicated GPU that would just compute global illumination and then feed view specific data to each client view rendering thread.
It would completely change the way you render games - right now most effects are done screen space because it's faster (eg. deferred shading) but if you could share world scene state you could get a lot more fancy with world space effects. Also the rendering pipeline would need to be a lot more asynchronous to avoid latency (eg. global illumination could be a separate process that would sync occasionally and not every frame to avoid extra latency in a trade-off for lighting latency).
