My view on the "permissions" would be that it is a hierarchy -- everything "below" the stack inherits the same sharing.
But I had not considered the other option people might want (you can use stacks to organize various folders which have varying permissions). That's why it's a discussion forum
From an end user standpoint, I fail to understand how having the ability to share a stack would make usability any worse in Evernote....or make it "bloated". Select a stack, right-click, share stack. What about that fundamentally makes Evernote more difficult to use or what built-in UI concept does it break?