Japan's IPA (Information-technology Promotion Agency) include in their general application development guidelines that user ID's should not be email addresses f

Japan's IPA (Information-technology Promotion Agency) include in their general application development guidelines that user ID's should not be email addresses for the exact reason that they "are easy to guess". I spent some time arguing that this was a silly requirement but in the end I had to change my program to use non-email address user IDs (which no one can remember as they are specific to this application... )