How many simultanios calls can asterisk dial using callfil

Basicly I have this burning question as to how many calls asterisk and the cpu can handle while dialing out via sip, zap or pri. I have heard that if to many are made that it would crash a asterisk box. Not good if you want to use it in a mission critical function.

How would the call files be setup for more then one number to dial out at one time? I have seen the single dial examples and tested them. Also, is there a web script or application built to type in the numbers of have customer sign up for a mass call file dial out at a cirtain time?