Yes, Google have, sometime order me input hongxiaowan for username, sometime order me input hongxiaowangmail.com.

For groups, should let who have gmail.com just input hongxiaowan. For others, input email.

For all google services where it says email, and you have a Gmail account, you can just put in hongxiaowan, xuanjames or whatever your username is.

James Xuan

Thank you. How about add your description in a Yellow square below the login field?

Yes, they don't make it very clear at all! :)