Not Clever Enough

Have you ever use Oracle's Exp to backup a user? It will ask you to specify file name, export grant, yadda, yadda, yadda....

Just right before the end, Exp will once again request the user to enter the user name or press return to exit. Normally, if we were to backup a user call "sample_database", we will type "sample_database" at the end and when Exp request user once again, we will just hit the return key to start a process.

But... have you tried to enter the same user twice? Oracle's Exp will just cleverly export the user twice, making the size of export double as well.