Haven't tried it yet, but seems feasible as far as I can tell you could build a spare computer to be used as a local area network ram drive.
After looking around and figuring out ratios number on bits to bytes it looks like
1000mbps (full duplex ie teaming)=250MB/s
2000mbps (full duplex)=500GB/s
10gbit (full duplex)=2.5GB/s
another thing to take into consideration though is the NIC connection bandwidth itself
PCI-Express x1=250 MB/s
I'm not too sure if or what bandwidth for onboard 1000-2000mbps LAN is, but I'd guess the same as PCI or maybe higher if we're lucky hard to tell either way it would be depends on both computers so any bottlenecks between them would slow the other down, but 1000mbps doesn't saturated PCI bandwidth and equates to 125MB/s which any way you look at it is fast.
The current 4GB setup I'm thinking of would be $244.94 + shipping & handling which I could get even a little cheaper with a different cpu, ram, and board combination, but would lose a bit of future expandability and would run slightly slower if I intended to make it multipurpose system.
ddr2 400 starts out at a transfer rate of 3,200 MB/s with ddr2 1066 running 8,533 MB/s
So even a 10gbit connection will only give you a maximum of 1.25 GB/s or 1/3 of ddr2 400 speed. Count in network overhead and network latency and you'll probably see 800MB/s. Nowhere near whats needed to effectively run a modern computer for any kind of use.