[usmt dev] refresh my memory...

[Mike Schiraldi]

I'm starting to wonder why we don't just make <Addr, Type> our primary
key. It seems that there would only be a small number of cases where a
person would have more than one object of a given type. Usually when that
happens (when a person "wears two different hats") they use a seperate
email address for each one. 

Expanding past <Addr, Type> opens up a Pandora's box. If we make the key
<Addr, Type, Foo> to support people who want to have records with the same
Addr and Type, what happens when someone wants to support different 
records with the same Addr, Type, and Foo?

So unless someone can demonstrate that the extra functionality of allowing
multiple records to have the same Addr and Type is worth making things a
lot more complicated, i'm going to dump that support.