Muxtape is pretty fun.  But what would you wager is the service’s lifespan?  Does it survive through the spring? 

Currently, the notice on its upload page states, “By uploading a song you agree that you have permission to let Muxtape use it.”  Something tells me that it’s not my permission that matters so much as the copyright holders’.  

I imagine that Muxtape is relying on one of the safe harbor provisions of Section 512 of the DMCA; specifically, like YouTube/Geocities/Yahoo/etc., a service provider’s liability can be limited when it transmits certain material that is stored “at the direction of a user.”  This is how YouTube has continued to allow users to upload video—it’s up to copyright holders to search for their “stuff” and request YouTube to remove it.  Of course, YouTube has also been doing a better job of policing itself as of late—Muxtape has not (and perhaps should not).  Who wants to guess what percentage of .mp3 files uploaded to Muxtape so far were legitimately purchased and/or ripped?

If Muxtape doesn’t last much longer, the next logical step could be a pay-for-use service.  For a fee, you could maintain your own unique domain name and craft your mix based on an iTunes Store-sized repository of licensed .mp3s.