Amazon (NASDAQ: AMZN) used its fourth quarter earnings call last week to reveal an important tidbit: overall purchasing by Prime Instant Video streamers is more than twice that of the rest of the e-tailer's user base. As rivals like Overstock look at these metrics and prepare their own streaming services, this dynamic is interesting to pay-TV operators, who are now looking at even greater OTT competition. FierceOnlineVideo has a complete breakdown of Amazon's Q4 call here.