Comment from the user end: I am not the greatest fan of OpenID (try talking your grandma through getting one) but I agree that as long as you don't have a site where the user might have a real need for unique authentication information (eg. bank account), you should really consider something like clickpass.
I always try new sites if I can get in with existing authentication - and I don't always if I need to register. So it depends how much you care about uptake.
I always try new sites if I can get in with existing authentication - and I don't always if I need to register. So it depends how much you care about uptake.