Facebook CEO Mark Zuckerberg leaves the Elysee Palace after a meeting with French President Emmanuel Macron. Aurelien Meunier | French Select | Getty Images

It's hard to tell how much of this might be legal, experts say. "Cryptocurrencies are so new that the manner in which they're regulated or not regulated is still being sorted out," said banking analyst Bert Ely. Most cryptocurrency regulation so far pertains to securities laws governing speculative investments — which wouldn't come into play in the case of Libra's hard-currency-backed valuation. "Its usefulness really depends on how widely accepted it becomes," said Bruce McClary, spokesman for the National Foundation for Credit Counseling. "If you have acceptance from merchants and partnerships with payment transfer systems, I think it could have the potential to stand out," he said. "Early indications are that it has the potential to go mainstream, but really, time is going to tell." But McClary also sounded a cautionary note. "My concern is that when you put social media and your wallet into a blender, there could be some problems. First of all you want to make sure your financial transactions are secure and private," he said. McClary also noted that Facebook said one of its goals with the Calibra wallet was to keep people in its ecosystem for longer. "The initial intent is hoping this will get people to spend more time on its platforms. If people are spending more time on the platforms they're also spending more time in front of advertising," he said. For people with limited financial literacy or discipline, this could be risky, he said. "It might be tempting for some people to overspend the longer they spend on the platform knowing they have available cryptocurrency." But whether or not a critical mass of Facebook account-holders would use Libra — especially given the company's checkered record on user privacy — remains an open question. "It's difficult for me to see anyone who cares about privacy actually adopting this new offering, particularly given Facebook's laughable record on respecting their users' privacy choices," said Brian Krebs, a cybersecurity expert who runs the blog KrebsonSecurity.com.