Truncate customers magento
### http://www.magentocommerce.com/wiki/import-export_and_data_manipulation/removing_products_through_the_database
SET FOREIGN_KEY_CHECKS = 0;
TRUNCATE TABLE 'customer_address_entity';
TRUNCATE TABLE 'customer_address_entity_datetime';
TRUNCATE TABLE 'customer_address_entity_decimal';
TRUNCATE TABLE 'customer_address_entity_int';
TRUNCATE TABLE 'customer_address_entity_text';
TRUNCATE TABLE 'customer_address_entity_varchar';
TRUNCATE TABLE 'customer_entity';
TRUNCATE TABLE 'customer_entity_datetime';
TRUNCATE TABLE 'customer_entity_decimal';
TRUNCATE TABLE 'customer_entity_int';
TRUNCATE TABLE 'customer_entity_text';
TRUNCATE TABLE 'customer_entity_varchar';
SET FOREIGN_KEY_CHECKS = 1;