A little over a week after Apple announced that the 45 billion App Store downloads mark had been passed (which took just over 4 months to get from 40 to 45 billion), the count down for 50 Billion downloads has begun. As with the previous grand giveaways, the lucky person who downloads the 50 billionth app will win a $10,000 App Store Gift Card. But as an added twist, the next 50 iOS users to download an app will also score a $500 Gift Card. In other words, the contest will end after the 50,000,000,050th app has been downloaded. For the complete details, head over to the 50 Billion Downloads page on iTunes, where you’ll also find the Top 25 Paid/Free iPhone and iPad apps of all time.