According to research from ZDnet, people download apps from the Apple Store faster than they buy McDonald's hamburgers. It took Apple just three years to reach the 15 billion app downloads milestone, and Apple is projected to reach 100 billion app downloads within 5 and a half years. It took McDonald's 46 years to reach the 100 billion hamburgers sold milestone. Check out the chart below for all the data and follow the preceding link to learn more about the ZDnet study.

Of course, its important to point out that most downloaded Apple apps are free while McDonald's hamburgers are not, but there is clearly widespread interest in mobile apps for Apple devices. The question is whether or not this fast growth would continue if all apps had price tags attached to them. What if more and more apps are released with price tags in the future? How will that affect Apple's speed at reaching the 100 billion app downloads mark?One thing is for certain -- mobile apps aren't going anywhere. It's likely more premium apps will be launched in the coming years and we're sure to see a proliferation of brand extensions beyond the mobile app market. The spread of the Angry Birds brand into merchandise, computer games, and a movie is the perfect example of how apps can reach beyond the mobile market into everyday life.In the meantime, other brands are seeing slower app growth. Even the popular Android brand can't keep up with Apple app downloads. We'll have to wait and see if that continues or if other brands can step up their offerings to lure more developers and consumers to their devices and apps.What do you think of the incredible popularity of Apple apps? Will this explosive growth continue for the long-term? Leave a comment and share your thoughts.