When product attribute has no default value, but in a specific store level or website level the attribute has value. When get Product Collection with the store level, it will not get the value.

bug in:

Mage_Catalog_Model_Resource_Eav_Mysql4_Collection_Abstract :: _getLoadAttributesSelect()

$select = $this->getConnection()->select()
                ->from(array('default'=>$table), array($entityIdField, 'attribute_id', 'default_value'=>'value'))
                ->joinLeft(
                    array('store'=>$table),
                    $joinCondition,
                    array(
                        'store_value' => 'value',
                        'value' => new Zend_Db_Expr('IF(store.value_id>0, store.value, default.value)')
                    )
                )
                ->where('default.entity_type_id=?', $this->getEntity()->getTypeId())
                ->where("default.$entityIdField in (?)", array_keys($this->_itemsById))
                ->where('default.attribute_id in (?)', $attributeIds)
                ->where('default.store_id = 0');

$select = $this->getConnection()->select()
                ->from(array('default'=>$table), array($entityIdField, 'attribute_id', 'default_value'=>'value'))
                ->joinLeft(
                    array('store'=>$table),
                    $joinCondition,
                    array(
                        'store_value' => 'value',
                        'value' => new Zend_Db_Expr('IF(store.value_id>0, store.value, default.value)')
                    )
                )
                ->where('default.entity_type_id=?', $this->getEntity()->getTypeId())
                ->where("default.$entityIdField in (?)", array_keys($this->_itemsById))
                ->where('default.attribute_id in (?)', $attributeIds)
                ->where('default.store_id in (0,'.(int) $this->getStoreId().')');