Well load balancing usually takes place in a router which then would be connected to both servers...so I dunno how exactly you could do that unless there are routers that can send traffic to a local server and remote server.
From an enterprise standpoint, I have used F5 products to achieve something like this. We also had some help from our ISP to span a public VLAN over a sonet ring.
The servers can be in different locations but they have to be connected in some way to load balance.
If they are great distances away load balacing may cause latency issues.
If they are close there are many NLB solutions. I dont have a specific rec. but there are some good ones