Google Page Speed and Yahoo YSlow deduct for scripts loaded in the document <head>. ScriptsDown modifies the DOM to move some or all of the scripts to the bottom of the <body>.
Whether providing tech support, testing a login, or testing a feature - at times, it becomes necessary to log in as a particular user. Do you know their password? Should you know it? Should you reset it?
With Authentication - As User - you don't need to know any password but your own.