What is the difference between graph-based databases and object-oriented databases?

Question

What is the difference between graph-based databases (http://neo4j.org/) and object-oriented databases (http://www.db4o.com/)?

Answer 1

With graph databases, you have a slight semblance of a chance that it is based on mathematical graph theory. With Object-oriented databases, you have the certainty that it is based on nothing at all (and most certainly no mathematical theory at all).