At Interbike 2011, I took a bunch of video of the lovely wooden bikes decorating the Kryptonite booth and talked with Kevin. He explained that Kryptonite's Bike Shepherd is a product which allows you to view information about a tagged and registered bike, via your cellphone, and then use social networking to help to return those bikes registered as stolen. (Watch the video.)
Yes, cats, if i were a bike thief, I'd try to scratch off the tags. Kevin told me that the glue is pretty difficult to remove. But I've peeled off so many bike wheel and rim labels, I'm pitbull relentless at label peeling. Bike thieves are sly, so use your collective urban cycling brains to place the tags in places someone can scan them with a cell phone, but where bike thieves won't immediately see them. (Suggestion: If you find an excellent and stealth place to stick at tag, don't publish the location online. Bike thieves can read, too.)