Biometrics should never be used for direct remote authentication. It suffers two major flaws:
- it must be stored in clear text or at least with an invertible encryption on the server - it has been discussed many times why it is not possible to store a hash of a fingerprint, mainly because what the captor sees may be slightly different on each time
- it cannot be revoked if compromised
So if one server has an image of your fingerprint to authenticate you, and if someone manages to get an image of it (from the server, from your passport, from a beer glass, etc.) he will be able to authenticate on behalf on you and the only thing you will be able to do is to find another authentication method.
The correct way (which is described on a Microsoft's page about that is to have a private key on a local system (say a mobile phone) and that key is locally secured by your fingerprint. But even in that case, all is stored on the mobile phone(*) (the private key, and an image of the fingerprint in an invertible form), so if it is stolen you must immediately ask the server to revoke the current key. The good point is that as the key is an asymetric key independant of the fingerprint, you can easily revoke it, and create a new one to use on your new phone.
(*) That means that is the phone can be unlocked with the fingerprint, you have not a multi-factor authentication system, but only a something you have.
That being said, for securing a local device, a fingerprint is probably less secure than a good password because it may exist on your passport and on the last glass you have used, but certainly more secure than a trivial one and at least you should never forget it...