An alternative that can really take the heat of a web service is the BOP Enterprise Bitcoin Server.
You can run several instances of it and send requests to them through a load balancing message bus.
See the example repository https://github.com/bitsofproof/bop-explorer that shows a simple REST API forwarding to the bus.
The server code is in https://github.com/bitsofproof/supernode
Bits of Proof will launch its offer in two days in San Jose, dramatically reducing the pain of integrating with the Bitcoin protocol.
Interesting so, I can run the server myself or is this a service being sold so I'd have to pay per request for example? Secondly, is there much in the way of documentation for the REST API? I'm assuming you don't have any other examples or libraries that aren't Java?