I think it might not be. Of course, what Sam means is "let us have all the RAM so you can run a ChatGPT client on your Commodore 64", and if that were the only thing RAM was used for, that would be more efficient. But it's not and it would be undesirable for things to become like that.

So let's imagine a general purpose RAM collective. I think for that to be workable at all, it would require a major upgrade to internet infrastructure to make it sufficiently high-throughput and low-latency, which would be very costly and also require a lot of RAM. The cost of all that would probably dwarf the inefficiencies of individually owned RAM not being used maximally.

Additionally, to get the latency low enough, the data centers would have to be pretty physically close to the people using them. But people who live near each other also tend to sleep, work and play at similar times, so the gained efficiency wouldn't be nearly as high as it could be. And on top of all that, even the lowest achievable latency would still be very slow by RAM standards, so at that point you might as well be using a hard drive as working memory.