I would think that the majority of the overall usage of kitchen knives would be true to the designer's intention. Given that this app is available on the iPhone App Store, which every immoral spur-of-the-moment teenager has access to, and will likely abuse, it is definitely something that the developers should have considered.
-- "Display a different number to protect yourself or pull a prank on a friend. It’s easy to use and works on any phone!"
Just because we can do things, and others do, means we shouldn't discuss the different use-cases and implications? I gather that most people are here to make a quick buck using their technical prowess, but to look away from possible misuse seems very shortsighted.
