That's how many times mobile apps have been downloaded between Christmas and New Year's Day. Let's try putting that in perspective.
According to Gigaom, there are estimated 150 million smartphones in the market by end of 2011. Let's say out of them, 70% of them were actively downloading apps (which I think is an higher-end estimate; about 50% of smartphone users are reported to enable WiFi
according to Nielson). That makes about 105 million smartphones and their users. If we assume one user one smartphone, it comes out to each smartphone user downloading about 11 or 12 apps during the last week of 2011 on average. These are new applications that people found somehow, probably through friends or media recommendations.
People are downloading new apps, and they are trying them to see whether it solves a problem at their hand. From the evaluation of the app to purchase and download, it takes a minute tops. And people are going through apps by volume (
All things D estimates average iPhone user downloaded about 83 apps in 2011).
Number of these downloads will likely increase, download will become faster, and time that you have to make the first impression will become shorter. Remember there are several other apps competing for user's attention per each week. If yours doesn't work, users will move on.
Your app is your new website. Build it, test it, and perfect it for those users on the go.