Google notify that in the "v13 AdWords API, requests that were made in excess of the limit were queued on API server until they could be run, resulting in what seemed like very long execution times for some requests. new API doesn't process these requests and instead returns a SOAP fault containing a RateExceededError (formerly QuotaExceededError in v200909)."
We believe this's an important feedback mechanism ensures your awareness of the issue and can adjust your applications accordingly. If you'e running into these errors often, steps should be taken to reduce the rate at which your app makes requests to API. One simple way to do this without sacrificing throughput is to increase the number of operations sent in each request. This allows you to get same amount of work done in fewer requests, reducing your chances of exceeding the QPS limit," explains Google.
More Info: Forum