From the forums
"...
Some of you are concerned about the technical challenges in making Native
Client secure. So are we, and that's why we are sharing the system in this
research release, so the community can review it with a critical eye. These
concerns have been with us from day one of this project, but as we continue
to work on the system we have increasing confidence in what we can do with
this approach. So, while feedback and discussion are very welcome, we also
hope our critics will show us specific design and implementation defects
that allow them to break out of the sandbox. Such specific defects are the
real key to whether or not we can make this system secure.
Thank you for your interest in Native Client.
Brad Chen"
Keep an open mind. This could be a very big.