My name is Adam Feldman, and I'm a product manager at Google. I see that you signed up for a key for the Google AJAX APIs some time ago and that you have a website or application making use of that key in server-side (RESTful) requests.
In order to help prevent legitimate queries that originate from a single IP address from being classified as automated queries, we are now offering a new URL parameter that may be used to identify the end-user that requested the query. You'll recall that our Terms of Use requires that every API request be made on the behalf of an end-user action, and this new parameter, 'userip', should be included with all server-side requests to help ensure that your usage of the API is not mistakenly identified as abuse.