Obama quotes Rick Warren's "Purpose driven life"

Did anyone else notice that when defending his choice of Rick Warren as the person to make an invocation during the inaugural ceremony Obama actually quotes a line from Rick Warren's book "Purpose driven life"? Obama speaks about disagreeing without being disagreeable. Sure, this is not a phrase copyrighted by Rick Warren. However, it is a phrase he really likes to use in his sermons, video presentations and, of course, his book:

We can reestablish a relationship even when we are unable to resolve our differences. Christians often have legitimate, honest disagreements and differing opinions, but we can disagree without being disagreeable

("Purpose driven life", p. 158).

You don't suppose Obama actually reads Rick Warren?