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Venntunes [iTunes link] is an extremely simple iOS app that let's you compare taste in music simply by bumping devices. After you bump with one or more friends, you will be presented with a list of artists you have in common, with the option to share that list via Facebook, Twitter, text or email, and find out more about the bands in question (and to buy tracks).
I am working from home today, so I could only test the app with my own devices, which is totally fine, since I already know I'm my own soulmate.
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