There is so much for a vegan blogger to say about this that it actually renders you speechless.
Here's a news story on this new menu item from the L.A. Times. That should cover the basics for you. Additionally, I'll let all the other vegan and diet bloggers do the ranting.
Here's my main thought right now - in 2010, when you're talking about the primary problems facing N. America, you're talking about climate change and health issues. And by health issues the big topics are the diabetes and obesity epidemics hitting both the U.S. and Canada.
Other companies are starting to see the light on the health front. Pepsi for example has recently dedicated itself to making all of its snack foods less "junky". The CEO has flat out said that they feel a certain amount of corporate responsibility for N. American health problems, and want to be part of the solution.
So this kind of thought is percolating in some company's head offices, but KFC? Well, KFC has suddenly decided upon a "What would Homer Simpson do" approach to menu planning.
A funny side-story to all this is that about a year or two ago, KFC in Canada succumbed to pressure from some animal rights groups, and started offering something close to a veggie-burger. The Double-Down must be their little "f*^k you!" to the forces that put a non-meat item on their menu.
