A great idea if you can have a time machine to go back ~6-8 years.
Perhaps a massive public startup investment at the start of what could be a long deep recession is not the best public policy.
I personally think that it will be a big plus for Silicon Valley. Some of Japan's best and brightest young people will see close up how the Valley works. Then they will go home, get frustrated and return to the Valley to start companies or work for startups.
Maybe. Or maybe they are investing to better come out the recession?