There is one upshot to podcast sharing, though: if you receive an audio podcast from a friend it won't be three-play DRMed the way shared songs are. (Say, do we smell some tracks-shared-as-podcast hacks coming on?) But there's a pretty big downside to podcast sharing, too.

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People using Askking Music can challenge their Deezer contacts and Facebook friends to identify tracks from shared favourites and playlists.

ENGADGET: Deezer App Studio goes mobile, brings apps to Android and iOS listeners

An algorithm tracks the velocity of FORBES content shared across the social Web.

FORBES: A Digital Home With 1,000 Doors

Combining IBM Research's expertise in the areas of mathematical sciences, computer science and high-performance computing with the deep-power engineering and operational know-how of the participating members, the Institute will focus on five core innovation tracks to pursue joint research and where shared investments, knowledge and capabilities will benefit every member.

ENGADGET: IBM announces Smarter Energy Research Institute, aims to improve energy grids (video)

The following list represents the most viral tracks on Spotify, based on the number of people who shared it divided by the number who listened to it, from Monday, May 13, to Sunday, May 19, via Facebook, Tumblr, Twitter and Spotify.

NPR: Spotify's Top 10 Most Viral Tracks

He can lead Americans of all races, religions, and persuasions, from students at Oral Roberts University to urban artists and musicians from the other side of the tracks in Detroit, in locking arms and marching together in a shared desire to solve our pressing problems in new and creative ways.

FORBES: Obama's Second Chance: Fulfilling the Untapped Potential