Is the Estate Tax Voluntary?

Professor Bainbridge looks at the Estate Tax and whether it truly is a voluntary one, something that if one is rich enough one can sidestep. I wrote about it here when Matthew Yglesias seemed to get a little confused.
My read on why the truly rich seem to be in favour of the estate tax is that they don't actually pay it, yet supporting it bolsters their liberal political stance. A full discussion of this was on sci.econ a few months back and the full entries are worth reading, here and here