$> some_command --username myusername --password mypassword

$> history

...

12345 some_command --username myusername --password mypassword

This comes up fairly often with poorly designed CLI's. Wiping your bash history after running the command isn't an unreasaonble hack.

Edit/Addendum: Although there are other (perhaps better) ways to achieve the same effect, the main point is that doing a "history -c" should be considered no more suspicious than e.g. closing a document to clear your "undo" history.