From Ajax Patterns
JSON is great to get data from the server side to the client side. But when you need to send data to the server side the advantage of using JSON is lost. In such cases UED or URL Encoded Data is a better method.
The basic concept behind this is that the most used data structures can be easily encoded into a URL. One can create variables, numerical arrays, associative arrays, multi-level arrays etc. using existing syntax. The best part is all the server side languages are capable of handling this format - so no parsing is needed.