Mumbai, June 20 -- Regulators will be watching closely when Facebook unveils its cryptocurrency project this week. Their vigilance is warranted. Mark Zuckerberg, the social network's founder, isn't going to gamble with what remains of his public image by replicating the worst excesses of the Bitcoin craze. He's not trying to create a speculative currency; a potential wave of mom-and-pop investment losses is the last thing he needs. He just wants a digital medium of exchange for use on his apps. Nevertheless, his bid to launch an online payments revolution carries plenty of risks, from antitrust concerns to the threat that it might pose to financial stability....