^This is exactly what give me pause to blindly swoon over Kurzweil's predictions: His achievements in other fields were at times good, other not-so-much, but really none of it carries over to his AI research predictions: It's a huge problem, much larger than the individual - a composite form of pattern acquisition, storage, search and association that deals with modeling all our senses, modeling our cognition, self-awareness, ethics, history, etc. I see his aim to "understand a sentence" (for his definition of 'understand') as a piece of string connected to a huge sweater: Pull just a little, and one finds it's connected to the entire thing.
When he compounds the (predicted) discoveries of nanotechnology and some form of artificial intelligence into all sorts of fantasy, I'm not able to suspend disbelief. If we replaced sections of your brain with machine replacements in tiny portions over time, so that you never fully realized the difference, there would be, in his words, "no death". I disagree: there would be several dozen post-operation mini-deaths where we didn't feel or act "the same anymore" to our peers or to ourselves. This is not extending life forever, this is converting ourselves into the v1.0 buggy technology equivalent, killing ourselves in the process. Is the "self" just the biology? No, but we're not going to have the first (or any) version of this concept work flawlessly. I envision Kurzweil's future not as sentient machines, networked together in a single giant consciousness - but rather a swarm of flawed algorithms flooding, corrupting the networks, flopping around with fatal bugs - like a post-op brain patient machine-zombie population. "There's Grandma - she got v2.4 of the Kurzweil artificial brain - yeah the one with the 'TakePillsAllDay' bug. We're waiting for a bugfix."