http://blogs.msdn.com/ecm/archive/2007/05/23/increased-performance-for-moss-apps-using-the-portalsitemapprovider.aspx
http://blogs.msdn.com/maximeb/archive/2007/11/17/blobcache-woes-how-to-work-clean-correctly-with-it-and-what-to-expect-when-using-it-with-sharepoint-features.aspx