The irony of the situation is that the xxx-in-1 developers now have a taste of their own bootlegging medicine, as after breaking the encryption the MAME devs can easily decompile and emulate their own code. The danger now though is that operation of bootlegs back in the day became commonplace and even acceptable in legitimate arcade venues, and unfortunately this trend is now back as many folks, even those aware of emulation's grey areas, are not aware of these xxx-in-1 boards' legality.
Many at the Replay show last year turned their nose up at the notion of emulation and avoided picturing PC-driven cabinets like ours, yet happily played and photographed multi-game board running cocktail machines without so much as blinking. If these xxx-in-1 boards are now gaining acceptance through ignorance, and MAME now emulates them and their custom game selection menu, there is a potential danger for PC's driving MAME to be installed in innocent-looking JAMMA cabinets and be ran coin-operated, for much less than the cost of a multi-game board, directly using MAME, and with a single coinage system running efficiently (something current front-ends don't do to discourage commercial activity like this). Worrying?