There are two arguments that are at the heart of criticising the feasibility of transhumanism. One is skeptical about whether we can gain the science to achieve this aim and the other asserts that, whilst the tech may be possible, human beings will use it to kill each other in vast quantities.

The latter seems a more fundamental problem with human nature. You want personalized medicine? That requires the wide distribution of Bio-tech printers - printers that would be just as happy to print out a lethal, tailor-made virus.

This argument is as old as the hills. But other than Totalitarian snooping on EVERYBODY - How do you prevent widely distributed uber-tech from being abused?