No, no, no, no no.
This would be a huge security risk. It would essentially allow anyone to create a ticket using any e-mail address and gain immediate access to all of the ticket history associated with that account.
See here for more info: http://osticket.com/forums/showthread.php?t=195(http://osticket.com/forums/showthread.php?t=195)
And also here: http://osticket.com/forums/showpost.php?p=8832&postcount=6(http://osticket.com/forums/showpost.php?p=8832&postcount=6)