This snippet shows how to change the name of a blog in the list of blogs that the user can write to.
// 100 is to do things last.
add_action( 'threewp_broadcast_get_user_writable_blogs', 'my_threewp_broadcast_get_user_writable_blogs', 100 );
function my_threewp_broadcast_get_user_writable_blogs( $action )
{
// Rename only blog #69
if ( ! $action->blogs->has( 69 ) )
return;
// Retrieve the blog from the collection.
$blog = $action->blogs->get( 69 );
$blog->blogname = 'This is the new name';
// No need to set the blog into the collection again since we are working with the reference.
}