The irony here is so thick we could cut it with a chainsaw. What are we talking about? Niklas Zennstrom and Janus Friis, the duo responsible for the former P2P app Kazaa that, let's face it, was never really used to download Linux distros and instead was the tool of choice for illicit downloaders, are stepping back on the digital music stage and launching a new startup called "Rdio."

Taking a page from Napster, Rdio is a legit service and will charge $5 to $10 a month for "unlimited access to music from your computer and mobile phone, even when you're offline." There will be apps for different smartphones, including iPhones, BlackBerry phones, and Android-based phones, and if you shell out the full $10, you'll be able to store and stream songs on these and perhaps other mobile devices.

According to The New York Times, Rdio will open this week as an invitation-only preview, and then become more widely available later this year, joining a sea of other subscription music services. Where Rdio will attempt to set itself apart is in its social element, giving users the ability to follow friends on the site, see what songs they're listening to, and view a list of the most popular music on your friends list.

Rdio Homepage