This works great for me in WP 3.9 with BP 2.0(?).
Super useful for situations like social login, where the user is not forced to supply any profile details that are normally required through the traditional registration process.
My suggestions would be:
1) An admin backend to configure the warning message. I find the default "banner" style very clumsy and overbearing, and the bg color isn't right for my site....will definitely be tweaking it, but I have to dig into the CSS. A simple admin interface with color picker, size settings, and the option to change wording on the message would make this downright awesome.
2) Make it obvious where the settings are (not) located. I know there aren't really any settings, but the page that says "there are no settings" is buried in the BP menu -- whereas the majority of plugins put their settings in the "Settings" menu. So I wasted a good bit of time hunting for settings, only to discover there weren't any. Maybe a message upon activation? or a link next to the name on the plugins page?
3) This would just be a major bonus for my use case: the option to force the "Name" field to contain a space, so the end user can't just leave their monolithic username as pushed from media. My users are expected to provide a full first/last name, and I'm ending up with all the social registrations having their username and "full name" match. Not quite what I was after! I'll be hunting for another solution, but it would have been great to find an all-in-one. :)
If 1 and 2 were done, this would be a 5 star app. Thanks!!