How secure it is to store a file on windows phone 7 and iPhone? 

As in Android, we have some file browser utility which shows all the files and folders stored on the sdcard of the device which allows user to copy, move, delete, and do other short of activities.

In case of Windows Phone 7 and iPhone, it seems there is no such file browser utility and I guess the storage architecture of these systems are different from Android which does not allows file browsing.

In my case for Android, I would encrypt the file and store it to make it more secure. I may also play with file and folder attributes.

For the case of iPhone and Windows Phone 7, do I need to encrypt the file and store it? 

OR

I can put file without applying encryption assuming that no other application will be able to access that file nor the user will be able to do the same?

What are the other alternates for securing a file on these devices?

Thank you