But that's why the abstraction is leaky. You no longer need to think at just the level of the abstraction, but also at the level of the implementation of the abstraction. This is fine, but it's one of the reasons abstractions tend to be less useful than they seem. If you're always thinking about what's really going on, you might as ditch the abstraction and only think about what's really going on. The less you have to think about its implementation, the better an abstraction is.
I sort of buried the lede in my comment... My main point was that while all abstractions are leaky, it's reasonable to judge them on the relative extent of their leakiness.
