Tweak's claim of "making each link at least six characters shorter than any other URL shortening service" is patently false. I just made a URL at http://u.nu and it was 14 characters long. Made one at Tweak and it was 15 characters long.

Also, this entire project seems astonishingly shortsighted. The .tk namespace is going to be chipped away by spammers until there's nothing left of it.