When you download the app, it shows what permissions are necessary to instal and run it. I'm not sure what iPhone users see, but droid users show them to you and ask whether you still want to install. Another thing that sometimes happens is that an app may have sane permissions to start, but an update down the road gives them access to the personal areas of your phone. That's where "uninstall" comes in handy.
Then the Grinch thought of something he hadn't before. What if Christmas, he thought, doesn't come from a store. What if Christmas, perhaps, means a little bit more. ---Theodor Seuss Geisel a.k.a. Dr. Seuss