The tougher she talked, the more skittish markets got. On April 26th, Merkel gave a speech in which she said, “Germany will help if the appropriate conditions are met,” making it sound as if that help were far from a sure thing. The yield on Greek debt immediately soared, and within days a rout was on. It may well have been the most expensive “if” in history

"I have had an interest in tracking oil companies (for crude) and refineries (for oil products) trading in their own volume over the past 11 years. As I noted last week (in "Oil Inventories, Speculation, and Hedging"), anecdotal evidence is already emerging that vertically integrated oil companies (VIOCs) – those controlling the upstream/downstream process from field to refinery through retail outlet – were unusually active recently in trading in near-month futures contracts in their own product.
This occurred both when crude oil and gasoline prices were rising (through close on April 29) and thereafter, as crude plummeted almost 15% and gasoline over 13% as of the end of trading on May 6."