An interesting article that I picked up off my friend Tony Wu's twitter. The underlying point - never underestimate dolphins just because they appear playful. Team leader Dr. Richard Connor says: "If you're going to run into your enemies, you better be with your friends, or have some that are close by, willing to be recruited."
In 2003 I actually had the great fortune of watching an incredible encounter between a group of dolphins and a sperm whale. I was sitting 80 feet above the water atop the crow's nest of the R/V Odyssey, essentially the best view in the house, and I saw this group truly harass a sperm whale. Every time the sperm whale tried to move forward, the dolphins would form a wall in front of it. They did this repeatedly until finally the sperm whale dived. It has intrigued me ever since.
Click here to read a news report on this research: http://theweek.com/article/index/226233/are-dolphins-the-gangsters-of-the-sea