This makes sense. However, the cops already have many peoples' fingerprints once they've been booked, and in general if someone wants your fingerprints they can usually get them. I think the question of fingerprint forgery is an important one but I would assume that in a real trial the evidence presented also considers the likelihood the fingerprints were forged.

That said, I can see how this could potentially dramatically increase the availability of public fingerprints if it were hacked. More importantly the fact you can't reset your fingerprint is something I overlooked. I do think that in general though anyone building a system that relies exclusively on a fingerprint as a highly hack-resistent security measure is foolhardy regardless of how prevalent fingerprint data is. In other words, your iPhone passcode isn't protecting your data anymore than your fingerprint if someone gets their hands on your phone, so I don't really see how this point is material to if it's a good idea to use fingerprints to unlock phones.