Google announced that it is adding a new parameter to the RESTful interface, userip for its AJAX APIs, due to abuse. With the new parameter, developers have the option of supplying the IP address of the end-user on whose behalf they are making the API request. Doing this helps Google determine what is legitimate server-sided traffic and what is abusive scraping.
Google says use of the new parameter isn’t required, but if it’s not included with server-side requests, those requests are more likely to be interpreted and automatically blocked as abuse. This is particularly true for situations where a server is sending a lot of traffic to the API.