Who knows exactly why things suddenly become popular. You could blame it on the media (although, as of now, there's a one less media outlet to blame), or you could blame it on the power of suggestion—a chef sees something on a menu someplace, it lodges in his or her consciousness, and before you know it they've put it on the menu at their restaurant without even realizing. Think of it like seeds scattered in the wind, trends moving from coast to coast.
In San Francisco right now, it's all about porchetta. I hadn't eaten porchetta in years, but all of a sudden it's turning up everywhere. It's the topping of choice on many a sandwich (Cane Rosso features it daily, and Kitchenette's been known to do a version), you can find it topped with salsa verde on the menus at Starbelly and Magnolia, and it's served with oversized white beans at the brand-new Ironside (which just started serving dinner). Consequently, that's how Poggio chef Peter McNee served it at the recent CUESA supper—sided by excellent wood oven-roasted tomato-sauced gigante beans. In other words, this is a bonafide trend.
And why not? The appeal of porchetta is obvious—it's boneless, it features supernaturally crisp skin that, ideally, shatters when you bite into it, and the meat is juicy, streaked through with fat and seasoned, typically, with garlic and fennel and rosemary. Porchetta as the new boneless, skinless chicken breast? Rise up, people, rise up! And chefs, should you want to get on the bandwagon, Ryan Farr has put together a very nice guide (if you are the squeamish type who doesn't want to see dead piglets, do not click.)