Amdahl's law is only relevant if you can't change your algorithms. If you can, then most of the time it's a non-issue.
The human brain runs off umptillion neurons each running at 100-1000 Hz (depending on measure). Not GHz, MHz or even kHz. Hz. Obviously it's an extreme case, but if general intelligence can be achieved without fast serial computing then there should be lots of things we can do with a few dozen cores all running at GHz rates.
That's bullshit. All of the programs I have written recently had an incredible speedup after porting relevant parts of the program from single-threaded to GPU.
Right now we are hitting the threshold of incompetent programmers and tools long before any other.
