Kendra Little has some thoughts on indexed views:
When I first heard about this behavior, it sounded like a bug to me: why should an alteration like adding a column to a view remove all the indexes?
A colleague of mine at Redgate wondered: is the behavior the same with the new CREATE OR ALTER syntax as it is with just plain ALTER? (Spoiler: I tested and it is the same: CREATE OR ALTER also drops all indexes on the view.)
Click through for the answer.