RAM bus speed is what - something on the order of 17GBytes/s. So a 10 Gigabit hub (which btw has to deal with collisions, errors, & other nastiness) is still an order of magnitude slower for bandwidth & you're probably still looking at 2-10x (if not more) larger latencies (which are what's really going to kill you).
It's still essentially swap - just maybe faster than current swap storage & that's a very generous maybe, especially when you start piling on the number of users sharing the bus and/or memory.
BTW - the 10 GigE interconnect isn't all that common yet & the cost of it + cabling is still up-there.
Compare all of this with just adding some extra RAM... I'm just not seeing the use-case. Either add RAM or bring up more machines & distribute your computation to not need so much RAM on any one box.