This idea is a little more contraversial and probably "out of scope" for Google Base. Nonetheless, I can see a few non-insignificant advantages. Allow Google Base records to link to other Google Base records. These links can be in one of two forms: 

• hierarchical and dependent
• explicit, via URI

Let's deal with the second form first. Google Base could define a new Attribute Type which defines a link to another record in Google Base. Then instead of (or in addition to) creating (say) a Google Base record for a course that lists the professor and the university, it could explicitly link to the professor and university records. Now we can start doing all sorts of interesting things with our data. Obviously, link consistency is a probably but given the fluid nature of Google Base's model, I suggest just letting the end user sort it out.

It would be nice, BTW, if these URIs could be written in such a way that they weren't dependent on having the record actually stored in Google Base. Perhaps this could be defined in terms of a URN?

The other type of link -- hierarchical and dependent -- would introduce a "container" attribute. Inside a container one could place a new set of Attribute values. When the outermost container is deleted, so would all dependent records. What does this get us? Well, it brings for example the Business Locations model back into the fold (especially if we implement simple structure also).