I found this fascinating quote today:
Moodle does a very good job of monitoring students, giving assessments/grades, providing content, and doing discussion forums. It does not do a very good job of synchronous collaboration, wikis, email, or any of the other things that Google Apps does an amazing job at. I guess that is why Moodlerooms decided that it would be a great idea to get the two projects together and create an easy way to do single-sign-on.learningischange.com, Feb 2009
You should read the whole article.
I found the article via Heather Sullivan on her FaceBook post from FriendFeed. Since many districts are looking to merge products into a single housing site for parent, student, teacher, and administrative access, Moodle partnered with Google just got so much better.