OK, let's go. All actionscript 3. If you create a Sprite and
then add a RadioButton as it's child (or a TextField - probably any
component) you will see that the Sprite now has a 100px height if
you trace it, even though the RadioButton is only 22px tall.
So what? Well, if you set that Sprite as the source of a
ScrollPane, the scrollbar will turn on too early, and you will get
a huge, empty scrollable area below the RadioButton.