I've submitted this as a defect under the iOS dev program. We'll see if Apple responds with 'as designed' as I suspect they will.
No, this is clearly a bug.
Some times the apps drops you back to the login screen, keeping your account ID but prompting for a password. This is how I suggested it is designed to normally work.
Other times however, the app drops you back to the login screen but clears the account ID as well. Most times it does this for me it also actually closes the complete app. I see a tiny instant of the app and then it appears to crash. When you open the app again it has the account ID cleared. I doubt the app is "designed" to work like this, it is indistinguishable from an app crash which is what I suspect is actually happening.
This has happened for me since the free find my iphone was announced but I could never find anybody else complaining about it on the web until today when I stumbled across this thread. It is *very* annoying. I have deleted the app (to clear its data) etc but no difference.
My email address/account id has a dash ("-") in it. It's not that simple is it?