Perhaps another possible reason for the apparent lack of extra-terrestrial civilisations is due to the existence of a probability barrier known as the Great Filter, which stipulates that their emergence within the galaxy is a hugely improbable event. There are a couple of very good YouTube videos which talk about it.
Basically it boils down to this, either
The Great Filter is in our past, and therefore we probably have the whole galaxy to ourselves (along with other extra-terrestial life that never made it past the single cell stage).
The Great Filter is in our future, and so we are doomed. Finding out the true nature of this Great Filter should therefore be the top priority of 21st century humanity.
In either case I think the Great Filter theory would explain quite well the lack of any Type-III civilisations within our extra-galactic neighborhood. The jury is still out as to whether or not Type I or Type II's exist within our galaxy though.
RE: The Von Neumann Problem - Where Are All The Aliens?