$attribute   = Mage::getSingleton("eav/config")->getAttribute("customer", "karma");
$used_in_forms=array();
$used_in_forms[]="adminhtml_customer";
$attribute->setData("used_in_forms", $used_in_forms)
    ->setData("is_used_for_customer_segment", true)
    ->setData("is_system", 0)
    ->setData("is_user_defined", 1)
    ->setData("is_visible", 1)
    ->setData("sort_order", 200);
$attribute->save();