BuddyPress.org

The simple fact is that you need the common hook, “, in footer.php of all your themes so that the bp admin bar will show up in user blogs in the same manner — inserting the bp admin bar at top of screen and pushing down the layout in the right amount.

There will be a couple or so themes where it won’t look the same because of style done on body/wrapper area. When that happens, ask WP.org forums or here to help you out with the CSS of that specific theme. Or, you can install the Firebug add-on for Mozilla and work on the style for those themes yourself.