It's a good thing that apps don't take up any physical space. If they did, we'd be up to our ankles in rusty iFarts and buggy home screen widgets. A new Localytics study shows that 26% of new apps are never opened a second time.
Download numbers only matter so much. If you have an ad-supported app, you need people coming back again and again to make any money. For the people who make pay apps though, this might not be bad news. It suggests that people are rather frivolous about their app downloading habits.
This trend has been on the rise since the start of 2010. We've all had it happen. You find some neat "time-saving" app or organizational app, download it, and promptly shelve it forever because change is tough. I'd be interested to see what percentage of these "one-time" apps are exercise or fitness-related.