Can you think of graffiti? Graffiti (singular: graffito; the plural is used as a mass noun) is the name for images or lettering scratched, scrawled, painted or marked in any way on the property. Graffiti is any marking of the public who may appear in simple forms of written words to elaborate wall paintings. Graffiti has existed since ancient times, with examples dating back to ancient Greece and the Roman Empire. (Wikipedia.

The iOS architecture of firewalling file system access for each application makes huge sense: it eliminates the means by which malware can attack the data of other programs. Apple could relax those rules at some point; the greatest speculation I hear is that there will be a DMZ where files could be moved from one app to another. This is a far better strategy than having a promiscuous operating system and try to add the protection afterwards.