Even without Trump's negative tweets, companies like AMZN are extremely overvalued and the premium is there on the expectation of future hyper growth. With the overall markets falling, investors are now taking a step back and re-evaluating their portfolio.

Also, with a possible trade war scenario happening, AMZN will no doubt be impacted. Ecommerce will also suffer as a whole, especially with a lot of products sold that are being manufactured in China.