It's not a service I'd use, but I believe that it's the kind of service that is vital to the Web's health. The ability of end-users to avail themselves of tools that decomopose and reassemble web-pages to their tastes is an issue like inlining, framing, and linking: it's a matter of letting users innovate at the edge.
An Internet that allows people to create these features and people to choose to use them is infinitely more useful than one where copyright or trademark bullies can prevent us from doing so. More nostalgia: Link-it-all.
Update: Scoble asks whether Cory would feel the same way if Microsoft tried its own proxy. I can't speak for Cory, but I would support a Microsoft tagger/linker/proxy alongside one from Google (and from EFF, and MPAA, and anyone else who wanted to write one). More options for end-users is a good thing. Provided users have market choices, and know about those choices, they should be free to exercise them.