I can't believe what I'm reading in all these answers. Not a single person has referenced Apple's HIG.
Resist the temptation to display your logo throughout the app. Mobile device screens are relatively small, and every occurrence of a logo takes space away from the content that users want to see. What’s more, displaying a logo in an app doesn’t serve the same purpose as displaying it in a webpage: It’s common for users to arrive on a webpage without knowing its owner, but it’s much less likely that users will open an iOS app without seeing its app icon.
You can't look at small time apps and get good ideas. That's the blind leading the blind. Look at these:
Weather in iOS7
Maps in iOS7
Mail in iOS7
Calendar in iOS7
Facebook on iOS
Where is their logo? It's on the icon you clicked to launch the app!
Now, compare that to the Yelp app. Yelp looks antiquated the wasted screen space and redundancy. (Notice "Nearby" is on top and bottom!)
Yelp on iOS
Mobile apps are different from the web in that you don't end up on an unknown app by clicking a link the way you do on the web. You get into an app by making the conscious choice to install the app and click it's icon. Now, if you are making a special app for handicapped people with short-term memory loss, that's a different story.
