The stock's premium valuation is becoming increasingly difficult to justify.The Trade Desk (TTD -1.95%) shares were slammed on Wednesday after Netflix (NFLX -3.40%) said advertisers will be able to buy Netflix ads programmatically through Amazon's (AMZN -0.11%) demand-side platform (DSP) later this year -- just on time for the holidays. For the independent ad-tech leader, whose software helps brands and agencies buy digital ads across the open internet, this is not immaterial. It puts a deep-pocketed platfo ...