Dark pop/soda (aka cola) is mainly made of phosphoric acid. It is literally an acid and if you remember your high school chemistry, you may remember that acids like to balance themselves with bases. Thus, when you drink a glass of pop, your body has to find a way to neutralize it. As such, your body takes some neutralizing calcium (a base) to neutralize the pop (an acid). Here lies the problem: your body retrieves the calcium from your bones. Pulling calcium from bones makes them weaker over time, resulting in bone weakness and possibly increasing the risk of bone fractures (hence this post's title, pop makes your bones pop).
Well, my bones are screwed... I spent most of my teen years guzzling Vanilla Coke and Pepsi Twist. Opps!