I'm working my way through Wilkinson's graphics book, and right there, on page 404 (could there possibly be a better page for this?) is this:
"The price paid for this efficiency is the loss of flexibility. We cannot examine relations not represented in the hierarchies. Navigation through OLAPs is quite difficult, which is why so many graphical models for representing them have been proposed."
Now, this is a graphics coding guy; he created SYSTAT. He's not, so far as I know, an RM guy. But he gets it.