This might seem very interesting at first glance, but infact even in nutrition and health news the same stories can repeated over and over in different guises. The fact that cocoa has beneficial antioxidant properties is not new news at all and has been known for several decades. I guess what made this particular research newsworthy is that the individuals in the studies got a health benefit from eating chocolate bars, which are traditionally seen as an unhealthy food.
To be fair the article does point out that there are other negative healthy consequences from eating chocolate and suggests that chocolate could be used in future to help prevent cardiovascular disease if the bars could be made with less sugar and fat - this seems a strange remark given that reasonably low sugar dark chocolate is now readily available (Lindt even does a 90% cocoa bar) and that cocoa powder and cocoa nibs are also readily available for baking and using in cooking, making it totally possible to make low-sugar, low-fat, cocoa rich recipes (see links at the end of this mail).
These attention grabbing headlines on health stories can unfortunately trigger food fads where people then start eating the latest 'superfood' in vast quantities. However, as with all foods, it's important to eat them in moderation and it's worth pointing out that cocoa isn't 100% good for you. Alot of people have cocoa allergies or intolerances causing symptoms such as migraines and acne. In addition they affect neurotransmitters in the brain and as a stimulant can disrupt sleep and up heart rate - I certainly feel this when I've eaten too much cocoa and can go a bit manic!