However, your fingerprint is a username in that case because it is all over the place. The police already have it. Don't be fooled, there are certainly kits being sold to law enforcement to dupe TouchID. You're data is less protected from those that you'd probably prefer not have easy access to it now.
Outside the HN bubble, this is an acceptable tradeoff. People who are concerned can continue to use passwords.
Therefore it is up to us to make the right choices. That we aren't doing it, choosing instead to defend flawed technological improvements and the companies doing it, is very regrettable.
> This is a disadvantage only when you are on trial. That's a pretty extreme contingency
No dude, that's not the only thing that can happen and it's in no way extreme. Many people do go on trial for trivial things (because shit, in the US at least, suing people is a way of life) and your laptop or phone contains your most secret conversations and desires, being the ultimate incrimination tool, a digital fingerprint of your own mind.
And you don't have to be on any trial. You don't even have to be a suspect in an investigation. It can happen and has happened for laptops or phones to be seized for inspection during routine filters, like by the airport security.
Also, in the US you may live under the rule of the law. What about countries where oligarchies rule, countries where corruption is the norm? What about countries like Rusia, China, India or Brazil?
Just today I read about a story about this traffic cop from my own country that had the bad inspiration of doing his job by fining his own boss for ignoring a red light and exceeding the speed limits. He was later accused of all sort of bullshit and had to fight it in a court of law for 2 years before he was exonerated.
And technology evolves and our devices are gradually becoming our stored memory. What do you think these corrupt officials or organized crime syndicates could do with your own mind, 10 years from now? A lot dude ;-)
I'm glad you have been deemed worthy enough to make that decision for the rest of the population that doesn't understand the implications of what they are getting into.