Here:

http://sentientdevelopments.blogspot.com/2007/08/fermi-paradox-self-destruction-or-non.html

To quote:

The past 40 years of scientific progress has forced a re-evaluation of humanity’s potential. We appear to be headed for a transformation that takes us away from biological existence and towards a postbiological, or digital existence. Our future visions must take this into account. As Milan Cirkovic and Robert Bradbury have noted, we need to adopt a digital perspective (pdf).

Why leave the local system when everything can be accomplished at home? Localized existence may hold promise for all the aspirations that an advanced intelligence could conceivably conjure.

Specifically, advanced intelligences may engage in computational megaprojects and live virtual reality existences. It would be an existential phase transitioning into virtual space such that interstellar colonization would never emerge as a feasible option or experiment.

For example, advanced ETI’s may construct Jupiter (pdf) and Matrioshka Brains. A Jupiter Brain would utilize all the matter of entire planet for the purpose of computation, while a Matrioshka Brain (a kind of Dyson sphere) would utilizes the energy output of its parent star.

Determining an upper bound for computational power is difficult, but a number of thinkers have given it a shot. Eric Drexler has outlined a design for a system the size of a sugar cube that would perform 10^21 instructions per second. Robert Bradbury gives a rough estimate of 10^42 operations per second for a computer with a mass on order of a large planet. Seth Lloyd calculates an upper bound for a 1 kg computer of 5*10^50 logical operations per second carried out on ~10^31 bits – this would likely be done on a quantum computer or computers built of out of nuclear matter or plasma [see this article and this article for more information].

More radically, John Barrow has demonstrated that, under a very strict set of cosmological conditions, indefinite information processing (pdf) can exist in an ever-expanding universe.

This type of computational power is astounding and defies human comprehension. It’s like imagining a universe within a universe -- and that may be precisely be how it's used.