Pointing to data showing run-ups in foreign purchases of U.S. stocks before the 1987 crash, the dot-com bubble in 2000, and the 2008 financial crisis, Ed Yardeni wrote in his eponymous research newsletter, "Their buying has a record of being a contrary indicator. They tend to be big buyers right before bear markets."

While Netflix could see its subscriber numbers drop during a downturn, some bulls suggest the streaming service might be one of the last things people are willing to give up when their wallets get lighter.