Given Andrew's good question we decided to go to the source: Mr. Fred Reichheld himself. This is from an email Fred wrote me today in response to the post I sent him:
I agree that it is useful to gather the number of referrals a person claims to have made--but that is looking in the past, while growth is about the present/future. Someone who made six referrals over the past year but recently had a lousy experience (or found a better supplier) is not a promoter. I think the top priority should be to focus learning on the current (or immediate past like last week) and the near future--thus, the ultimate question works best as it is formulated in my book.
1) "Would you recommend us to a friend?"
2) "HAVE you recommended us to a friend?"
should be the ultimate question for customer survey
BTW - my vote is for #1