I am having a similar issue as described here, except not using buddypress, just multisite and the membership plugin. I know its a result of the membership plugin, because I was previously using and infusionsoft plugin which has this as one of its multisite bugs, and everything worked fine once i deactivated that.
So i get the email that a new blogis created, as the admin, but the user doesnt. This is problematic, because i cant expect that my users are going to remember their new URL, or how to log in to their new site. any way to make sure this email is still sent?
Im on WP 3.04, multisite, using membership plugin though the plugins directory only for the main site.