Use GeoPlanet to convert user-submitted locations into usable data such as latitude/longitude coordinates and city name. GeoPlanet is also available through YQL.
Reference yap_jurisdiction (an ISO 3166 country code passed as a post parameter to YAP apps) and Accept-Language (an RFC 2616 section 14.4 language priority list passed as a header to YAP apps).
Yahoo! provides built-in authentication and authorization support. If an App requires a user’s personal data, Yahoo! shows a permission screen the first time the user starts using the App. Once a user gives permission, the developer can use OAuth to access the user’s personal data. Yahoo! sends access token information each time the App is loaded.
User trust is essential for an app to be successful. Be respectful to your users. Design an experience that engages novices as they gain confidence with your app.
Don’t display sensitive or private information to others. (Example: “Mark just bought 4 shares of AAPL stock at $93.14/share.)