I use Emailtoid to create accounts in my Web site and it works very well. I find this solution very elegant, and as today OpenID is not well known for the public, Emailtoid is a nice simple solution. You can check here how it works : http://www.musiic.net/myartists/create.php5
And to create a Mixtape from MySpace artists, It is here http://www.musiic.net/myartists, the name is MyArtists, it is simple, easy and with the same mixtape interface (coming from Opentape)
About running OpenSocial applications in Facebook, I have already tested OpenSocket (http://www.opensocket.org/blog/), and it works well and it is a very good idea :) With project like that Facebook will have to move to OpenSocial, or in any case we will find ways to run our OpenSocial app on it.