Target’s new “Cartwheel” Facebook shopping app is a great concept – use the world’s most popular social media platform to help generate in-store traffic. But the execution is clunky. It kind of reminds me of the second “Star Wars” trilogy that came out around the turn of the millennium – the back story of Darth Vader was rich with potential, but George Lucas polluted a great dramatic story arc with floppy-eared aliens and lame attempts at political commentary.