If you need any more proof that the “stonks” effect is real, look no further than a chart of Costco’s stock price over the past week. You’ll notice a steep cliff that begins with the market open at 9:30 a.m. on May 18th, when shares were trading unexpectedly lower at $460, down $30 from close the day before. The plunge continued throughout the afternoon, ultimately landing Costco below $430 — down 13 percent of its value. Which it’s yet to recover. What caused the crash? A well-timed tweet from Twitter troll @JohnWRichKid, who disguised his account as a newswire service on the morning of May 18th to seed the fake ... (full story)