Pretty cool; Andy Wingo added sandboxed evaluation to Guile! Pretty cool! Some brave folks should try it on something, like an irc bot you can evaluate code on. Or add player-contributed scripting to Mudsync? :)

Also, a pretty good quote in there:

Sometimes you would like to evaluate code that comes from an untrusted party. The safest way to do this is to buy a new computer, evaluate the code on that computer, then throw the machine away. However if you are unwilling to take this simple approach, Guile does include a limited “sandbox” facility that can allow untrusted code to be evaluated with some confidence.

Maybe not safe enough! Did you wipe that computer sufficiently so as to avoid leaking information into its environment? :)