Only four weeks remain to migrate to Oauth 2.0!
Parts of the Account Authentication APIs (ClientLogin, AuthSub and OAuth 1.0) were officially deprecated on April 20, 2012 and will be shut down on April 20, 2015. We encourage you to migrate to OAuth 2.0 as soon as possible. You will get an error if you continue to use these methods beyond the final shutdown.
If you are using one of the Authenticated APIs, (Core Reporting API, MCF Reporting API, Management API, Provisioning API) you will need upgrade OAuth 2.0 as soon as possible. Note: Once you upgrade your users will need to reauthorize your application.
If you are using an unauthenticated API, such as the Metadata API, you still must register your application in the Google Developer Console and your application will need to identify itself every time it sends a request to the Analytics API, by including an API key with each request. Note: Previously, Google Analytics provided a very low grace quota to accommodate a small amount of testing, with this shutdown this will no longer be the case.