Very helpful tips above, thanks David!
To save new attributes in frontend (register and edit) simply expand the second array of parameters $ attribute-> setData as follows:
$eavConfig = Mage::getSingleton('eav/config');
$attribute = $eavConfig->getAttribute('customer', 'flavour');
$attribute->setData('used_in_forms', array('customer_account_edit',
'customer_account_create',
'adminhtml_customer'));
$attribute->save();
After that, you will find 3 new entries in the customer_form_attribute table instead of one.
If you want to test this before and after this change, just paste
Mage:: log ('attrib:'. (string) $attribute- > getAttributeCode());
371 app/code/core/Mage/Customer/Model/Form.php, . ( 1.4.2.0)