In early October 2009, a server malfunction or technician error at Danger's data centers resulted in the loss of all Sidekick user data. As Sidekicks store users' data on Danger's servers—versus using local storage—users lost contact directories, calendars, photos, and all other media not locally backed up. Local backup could be accomplished through an app ($9.99 USD) which synchronized contacts, calendar, and tasks, but not notes, between the web and a local Windows PC. In an October 10 letter to subscribers, Microsoft expressed its doubt that any data would be recovered.