Identify Portal Visitor Without Password Authentication

Hi All,

Is there anyway we can identify or authenticate a portal visitor buy let him entering only his login name (without a password)? The scenario is, there is a feedback application where the set users will enter their name and log the feedback. Since this is only about entering feedback on few things we don't want to bother the users to remember a password or to enter password but still we want to identify who enter and what.

Is there any workaround for this?

Thanks and Best Regards,
Ithrees