Energy is the limiting factor associated with any singularity
Ray Kurzweil forgets to think about the universe rationally... i.e. once you pass a threshold of intelligence that is the singularity of knowledge, there is no reason to increase the amount of computation going on in the universe unless you wish to for some particular reason or to increase or decrease the flows of energy in particular ways or for some end. Beyond that, the rationality he has is limited to **clean** environments or those that don't have any retarding factors... once you add in the fact that life is an extension of the same principles existing at all levels of the universe, you now have nanobots competing with everything else for the same energy sources as everything else. Just the fact about nanomaterials are game changers in everything from chemistry to toxicity doesn't do much except make them more of a problem -- I mean, take an explosive, replace standard compounds with nanotized versions of those same compounds and you get several factors more force out of the result -- meaning one could theoretically make whatever much smaller. Taking extreme cases for the sake of Jesus Christ, of course.
If you push the energy in one way or another, you usually have to control the push in that direction and that takes energy. To keep a system clean or to prevent decay or to repair the damage done by constant variations, etc etc takes energy.
The result is the same, energy is the limiting factor associated with any singularity... If we go to the next level, something like Dyson sphere level of energy control, the capabilities within reach are beyond most people's imaginations... But given that humans can't even utilize the energy we have efficiently, the results of giving humanity that level of energy is negligible to the results one seeks if it is for the betterment of humanity... Higher levels of control over our environment? You mean greater amounts of energy being used to buffer the extremes ... this induces a secondary problem associated with less variance in the extremes, more stability results in a greater amount of organisms at that threshold of energy conversion taking over all the sources of energy available and reducing the availability of surplus energy in the environment to life forms that tolerate and survive in across larger ranges of extremes to the detriment of stuff like bacterias and fungi etc.
Granted, there are supposed to be some super intelligent forms of intelligence by the time we meet the singularity - it is no longer 2020 yay? 20 more years lol. But seriously, the reality is that the next threshold of energy control will be reached and intelligence must either be increased across all humanity or we are just going to breed and increase the poverty numbers like in India or China... We (meaning those in countries with low population density) don't have to directly deal with running out of water (we bottle ours and charge $3 for a serving, talk about a business to get into!) or finding a shelter that is relatively safe from wars and people running around with explosives so psychologically unstable (from not getting enough protein, getting diseases/viruses, etc) that they want to blow up everyone else because their sister or brother died or worse some religious nut used their weak psychological state to make them a walking time bomb of stupidity...