A major, avoidable error by Microsoft caused the permanent Sidekick data loss from over a week ago, sources said this weekend. Multiple tips to Hiptop3 claim that Microsoft had no backup of the Storage Area Network (SAN) used to hold Sidekick information and lost the data when Hitachi encountered a failure during an upgrade. The company may now have little choice but to start fresh and have users re-sync data from their Sidekicks once a fresh SAN is ready.