Kurzweil presents many convincing arguments, but the central tenet is that the doubling of processing power keeps up for another two decades. Due to the nature of nature, what we observe as exponential growth in the end invariably turns out to be logistic growth. If this is so, then at any time the doubling of processing power could slow, and this would mean that we would only, at the most, get one more doubling. Such an event would bring the dream of a near-term universe full of computers to a screeching halt.
I believe that we should be able to create machines that think, but it is important that we aren't blinded by ideology. A massive "singularity movement" that ends up disappointing people, will in the best case delay the advent of such technology due to funding issues. I think the history of AI has demonstrated this quite clearly.
If Kurzweil's estimates are correct, though, another 8-10 years of "exponential growth" in computer hardware will put full-scale simulation of a human brain into supercomputer territory. And frankly, I doubt that evolution has managed to find the most computationally efficient way to achieve intelligence. There's got to be a way to do this.
I was actually just wondering why this project wasn't happening yet while reading "The Singularity is Near". If you haven't read it, I recommend it. It's hella dry and boring in parts, but overall worth reading if only to make you think about what a startup might look like in only 5 or 10 years.