Facebook is retooling its famous "hackathon" all-night coding workshops to give engineers more time to conceive new products, hopefully with a focus on mobile. The hackathons, a longstanding event at the company where "hacking" is central to the corporate mantra, have previously run as anything-goes, all-night workshops in which employees think up new product concepts and develop rough prototypes. If they impress, those prototypes sometimes end up as commercial products.