Can I control when gwabbit pops-up for new contacts?
Yes. From the main gwabbit screen of the gwabbit application, you can set the automatic notification (“prompt me when a message contains a signature”) to “only if it contains new or updated contact information” so gwabbit won’t pop up for contacts already in your address book with the same information; or to “never” so you can launch gwabbit manually only when you choose to gwab a contact.