Digital currencies are generating a lot of excitement. John Oliver enlists Keegan-Michael Key to get potential investors equally excited about the concept of caution. Connect with Last Week Tonight online... Subscribe to the Last Week Tonight YouTube channel for more almost news as it almost happens: null Find Last Week Tonight on Facebook like your mom would: http://Facebook.com/LastWeekTonight Follow us on Twitter for news about jokes and jokes about news: http://Twitter.com/LastWeekTonight Visit our official site for all that other stuff at once: http://www.hbo.com/lastweektonight