Consumers spent more than $1B of cryptocurrency globally on goods and services through crypto-linked cards in the first half of 2021, Visa (V) CFO Vasant Prabhu told CNBC in an interview.The credit card payments network estimates that consumer crypto spending was only a fraction of that amount in 2019."People are exploring ways in which they can use cryptocurrencies for things they would use normal currencies for," Prabhu said. "There are lots of issues in terms of volatility, etcetera. But that's up to the owners of cryptocurrencies to manage and track."The company also announced that it will add the FTX crypto platform, founded by billionaire Sam Bankman-Fried, to its Fintech Fast Track Program, which focuses in part on making cryptocurrency more practical for consumer and business spending.BlockFi, Coinbase, and Circle are current Visa partners that allow card holders to spend from their crypto wallets at more than 70M merchants.Crypto-linked cards and