This book has gone through several revisions and three editions, and I thank many contributors, readers, and colleagues. I would like to add thanks to Tonya Engst for her almost literal tireless work in churning through these editions and the details involved. Thanks to Adam Engst, also, for his help with the media chapter of the book. The virtual thinness of this edition could not have been accomplished without Apple having listened to its customers, and fixed numerous bugs, while filling gaping holes in sharing services. Thanks, Apple!