It is a well advertised best practice to configure maintenance plans for SQL databases forming the data layer of SharePoint deployments. How critical is it to monitor and reduce fragmentation of the databases and indices (indexes)? How to do this?
I can follow up on your own answer with these articles from Kimberly Tripp:
There is a Microsoft whitepaper on the topic and a knowledge base article: Database maintenance for Office SharePoint Server 2007, 932774. Personal experience sharing will be appreciated.