I'm not sure why, but I've never heard singularitarians consider that computation and intelligence is bounded by more hard constraints, like physics, than will let exponential growth continue indefinitely.
Um, just read the linked article. "The population of smart machines would explode even faster than the economy. So even though total wealth would increase very rapidly, wealth per machine would fall rapidly." Robin Hanson is not a self-declared "Singularitarian", but I, his co-blogger, certainly am, and we had a discussion about the effects of future resource constraints on intelligence here:
Of course, but we're not anywhere near the physical limits. An analogy is that it's clear that molecular nanotechnology is feasible, and consistent with known physical law, even though we don't know how to engineer MNT systems.
The "extrapolation of exponential growth = 'Singularity'" idea is a really crappy argument, and you shouldn't give much weight to it. For me it comes to two postulates: 1. AI is feasible. 2. When AI arrives on the scene, large changes are in store.
But I'll play my bets and say that NP-Hard will stay hard, the speed of light won't be broken, and at a certain point you need to switch to reversible computation because of landauer entropy, which will set space constraints of it's own.
