This article in Scientific American titled "Can sitting too much kill you?" is the boost I need to get off my butt and make a treadmill desk.
[E]ven if you are meeting current physical activity guidelines by exercising for one hour per day (something few Americans manage on a consistent basis), that leaves 15 to 16 hours per day when you are not being active. Does it matter how you spend those hours, which account for more than 90% of your day? For example, does it matter whether you spend those 16 hours sitting on your butt, versus standing or walking at a leisurely pace? Fortunately or unfortunately, new evidence suggests that it does matter, and in a big way.
...to quote researcher Marc Hamilton, sitting too much is not the same as exercising too little. (if you take only one thing from this post, let it be that quote from Dr Hamilton).