News map (from: Google)
What worries lawmakers is that most consumers don’t understand the application.DevelopmentHow to use email content. Three senators said that Google may not have taken sufficient measures to protect Gmail data and asked the company to disclose all instances of application developers sharing third-party Gmail data with third parties.
Although Google itself no longer scanned user email content for advertising purposes a year ago, it continues to allow hundreds of external developers to scan Gmail user inboxes. These services typically use free apps and offers to trick users into agreeing to access their inbox, but they don't clearly state what data they collect and how to use the collected data.