Here a non-scrollable version, all items are visible though smallest nodes tends to be a little too small, but it looks like a tree map:

Here is the same tree map but twice as large and scrollable like the Windows 8 UX-style, now items are larger but size differences are less obvious between them. And as a side-effect, since the tree map has more space, it tends to squarify the items making it look like more a grid than a tree map:

Question:

Do you know if there has been any research on the question that whether tree maps should be scrollable, or not ?