Biometric authentication has a role in maintaining and defending our control of our own identity and personal data. This emerging technology makes it virtually impossible to assume someone else's unique identity.[From Understanding anonymity and the need for biometrics | The Industry Standard]
But biometric authentication of what? If it is biometric authentication of a single, unvarying, "full disclosure" identity (eg, a national ID card of some description) then it's hard to justify the architecture. In other words, why bother with authenticating people against some identity token when you can just match them to their identity in some sort of database: instead of showing the supermarket an ID card to prove you are old enough to buy cigarettes, why not have the supermarket send your fingerprints off to a database and have the database tell the supermarket how old you are? There's no need for card. Or is there?
We have to expect that people will see us when we are in public and that our open public acts will be just that. But we have to worry that, in an anonymous world without authenticated identity, privacy will be violated when others can assume our identifying characteristics and take control of transactions and interactions outside the home that are indeed personal and unique to us.[From Understanding anonymity and the need for biometrics | The Industry Standard]
With the right identification and authentication architecture, the card provides a means to prove authentication without necessarily disclosing identification. Thus, my ID card can tell you that I am its rightful owner (by matching my, say, fingerprint with an on-card template) and that I am 18. But there is no reason for it to tell you who I am.
So are biometrics good or bad? Again, let's use this phrasing: if biometrics did work properly, what are the implications for the connection between real identity and virtual identity? One thing to bear in mind is that the systems are used by real people. If we implement biometric systems, we'll get results that have nothing to with the technology (or privacy) and everything to do with human nature:
However, according to senior officials those employees who have been forced to come on time due to the biometric way of attendance are trying to `sabotage' the machines.[From Glitches galore in MCD biometric machines-Delhi-Cities-The Times of India]
On balance, I think I'll come down on the side of "help", because there is the potential to implement useful systems in a privacy-enhancing way, even if it is not currently being fulfilled.
These opinions are my own (I think) and are presented solely in my capacity as an interested member of the general public [posted with ecto]