Implement "favourites" Feature?

I have written a dynamic database driven, object oriented website with an administration frontend etc etc. I would like to add a feature where customers can save items as "favourites", without having to create an account and login, to come back to them later, but I dont know how exactly to go about doing this... I see three options:

Log favourites based on IP address and then change these to be logged against an account if the customer then creates an account;

Force customers to create an account to be able to use this functionality;

Log favourites based on IP address but give users the option to save their favourites under a name they specify.

The problem with option 1 is that I dont know much about IP addresses - my Dad thinks they are unique, but I know people have had problems with systems like this.

The problem with 1 and 2 is that accounts have not been opened up to customers yet - only administrators can log in at the moment. It should be easy to alter this (no more than a morning or afternoons work) but I would also have to implement usergroups too.

The problem with option 3 is that if user A saves a favourites list called "My Favourites", and then user B tries to save a list under this name and it is refused, user B will then be able to access the list saved by user A because they now know it already exists. A solution to this is to password protect lists, but to go to all this effort I may as well implement option 2.