> and it’s not sufficient for Microsoft or whoever to day “oops too bad, you built on a private API” because ultimately they would be disrupting their customers

> and it’s not sufficient for Microsoft or whoever to day “oops too bad, you built on a private API” because ultimately they would be disrupting their customers. Uhhh, that seems perfectly sufficient to me. Play stupid games (like relying on undocumented APIs), win stupid prizes (like watching everything break when those APIs change). Private interfaces should be used as a last resort, and with the full understanding that - being private - they have no obligation to be "stable".