Hello,
This is a bug report and  feature request at the same time!
I use easy profile and I also use CMC Mailchimp from http://compojoom.com   Part of that extension is to allow a tick box  into the registration form for people to sign up to the newsletter. If I enable this plugin with easy-profile system and user plugins enabled, it doesn't show.  Turn them off and  it works fine.  So some kind of conflict I guess.
So, for the feature request, how about adding  in mailchimp integration during registration and when logging on via social network?  Not sure how complex that would  be to do?
thanks Pete