Why does my iPhone Gmail say archive instead of delete?
Apple has added support for Gmail's archive feature with iOS 4. When swiping across a message you wish to delete, the red button that appears says archive instead of delete.
To disable Gmail archiving for an account, follow these steps:
1. Navigate to Settings -> Mail, Contacts, Calendars
2. Select the Gmail account you want to change from archive to delete
3. Touch Archive Messages -> OFF