On the one hand, my first, gut response to something like "DARPA has a cool new search engine" is "well, they need to immediately make it publicly accessible and release the source code."
And in theory, at least, project manager Chris White is on the same page, saying "By inventing better methods for interacting with and sharing information, we want to improve search for everybody ..."
On the other hand, Memex seems to be all about searching, and searching for, information whose creators/curators aren't particularly interested in sharing with every Tom, Dick and Harry who might happen to be interested. So my equal and opposite reaction is "well, they need to immediately cut off law enforcement access to this thing, do a multi-pass deletion of every drive containing its code, etc." Cassius Methyl at The Anti Media seems to agree.
On the third hand (yes, I have three hands), if DARPA is developing this stuff, it can, and therefore will, be developed by others sooner or later.
So I'm back to the first hand. Unless DARPA went private-sector when I wasn't looking, this stuff is public property. Let's see it. Now.