Although I disagree with ChrisA's comments about the liklihood of uploading and its consequences, he raises an excellent point about AI - it seems like it will much easier to achieve than interstellar flight. This gives rise to the "transcendence" argument - that civilizations achieve AI quite quickly and afterwards become disinterested in space travel or communication because the rest of the universe seems trivial (easily computable) to them. This idea is vulnerable to the same "luddite exception" problem as the VR argument, though, unless AIs inevitably wipe out their biological precursors.