Part of the problem is we need storage. Another part is that we need uptime. Neither is really compatible with booting even from a USB stick - and really, that's out of scope anyway, that's something somebody should write who knows more about building operating systems than we do. However, we do take some precautions with regards to local security, and plan to take more in the near future. For instance, we tell the browser not to cache anything, we encrypt (optionally with a password but in any case easily got rid of) potentially incriminating data on disk, and we strongly recommend users install Truecrypt (since unfortunately we can't turn on swap crypto or lock pages in memory). A significant proportion of the community think taking any local precautions is a bad thing, since it violates the unix philosophy... As regards darknet, it is simply the only possible option in any even vaguely hostile regime. For instance, China has managed to block most of the Tor hidden bridges. Apart from that, it is also the only realistic option for really good security on Freenet: an attacker can connect to everyone, and Freenet's architecture on opennet isn't really suitable for dealing with this. It is of course possible for nodes to connect to both darknet and opennet, and the hope is that users will gradually add their friends as Freenet becomes faster, easier to use, more popular and has more content.