code: public function getBlockPath(Mage_Core_Block_Abstract $block) {
          $blockPath = array();
          $step = $block->getParentBlock();
  	$i = 0;
          while ($i++ < 20 && $step instanceof Mage_Core_Block_Abstract) {
              $blockPath[] = $this->getBlockInfo($step, false);
              $step = $step->getParentBlock();
          }
          return $blockPath;
      }
docs: Get path information of a block
  
  @param Mage_Core_Block_Abstract $block
  @return string
  @author Fabrizio Branca
  @since 2011-01-24