Before we start developing our OAuth application we applied for new API Key as everyone did. But the experience was a BIG frustration as it always displayed the red "Domain verification failed" error message although every detail has been carefully checked again and again during our applying process.
After trying at least 20 times we finally found the only *mistake* we made was writing the application name and description in Chinese. After we changed the application name and description to English, the domain verification suddenly succeed.
I think this should not happen since I believe we are developing an application that uses Unicode. Entering the application name/description in English also increases the chance that prevent our users from completing the login process because they see English, not their native language.