Here's how to do it: http://www.osticket.com/forums/showthread.php?t=1175(http://www.osticket.com/forums/showthread.php?t=1175).
Here are a few threads on why not to do it:
http://osticket.com/forums/showthread.php?t=2464(http://osticket.com/forums/showthread.php?t=2464)
http://www.osticket.com/forums/showthread.php?t=2585(http://www.osticket.com/forums/showthread.php?t=2585)
That would be a serious security flaw. For example to access all your tickets, all I need to know is your email address to open a new ticket and login. i.e osTicket uses email/ticketID combination for logins. The plan is to move to username/password in the future but still allow email/ticketID to view individual ticket.