Back in October, you responded to a similar request to the one I’m about to make with this:
“As for a login there is no customer login system and there is no plans to have one. We believe it creates to large a barrier to your customers.”
I would like to respectfully disagree. You’re right in that forcing a login would create a barrier, and using a cookie would probably be a poor solution, but I’ll tell you this: I love being able to login and view all my support requests without having to look up and enter some weird “code” to get there.
If you could set it up so that a login isn’t required, but if a Customer ID was entered, then it could require a login. You’d merely need to store a Customer ID-Password combo, and perhaps the Name/Email/Phone of that customer so they can enter a new case more easily, browse their open cases, that sort of thing. You could even work it in with the LiveLookup stuff if you didn’t want to store passwords and whatnot.
This can be done in an optional and non-obtrusive way, it’s just not a simple programming task. However, the really great features rarely are simple to write. 
I would be more than happy to work closely with you to get this working well, because I really think it’d be a fantastic addition.
Admittedly, I’m still reviewing your product (though I’m pretty sold on it, let me tell you!) but if you can tell me that you’ll seriously consider this it would be icing on the cake.