Yesterday was a bad day to be a laptop thief in Oakland, but a great day for the makers of Hidden, an app that helps you find your stolen MacBook. Hidden, a service that starts at $15 a year, leaves no visible sign that it's been installed on your computer, but offers a trove of information about who nabbed your machine. It sends you photos of the thief and his or her surroundings using the iSight camera; it uses advanced tracking to locate the computer to within a few meters; and it takes screen shots if you want to see what the thief is doing. (You might not.) The app got some spectacular advertising yesterday thanks to Joshua Kaufman's Tumblr blog "This Guy Has My MacBook." Kaufman posted pictures and screenshots showing the man who allegedly stole his laptop, and knew his location. Oakland police said they didn't have the resources to arrest the man, but sprang into action after Kaufman's site got some love from Gawker, Mashable and others. Late yesterday, they arrested him. But of course, the real star of this whole affair is Hidden. If you have a beloved MacBook, you might consider springing for the app. And if you like stealing beloved MacBooks, you might consider a new career of pilfering PCs.