Think of all the horrible uses this can and probably will be put to.
Government spy program will have records of everyone who's touched the device with timestamps and GPS coordinates.
Criminals will be harvesting IDs (Fingerprint + forward facing camera for face shot) for forged documents.
Decrease in overall security from people relying on one unchangeable password that is fairly easy to steal. Most people will undoubtedly think of fingerprints and the end-all-be-all of digital security when in reality it's only useful as an additional layer of protection. There will be apps that will store all your passwords with your fingerprint as the master making access to all your accounts as easy as taking a glass you've used or even dusting your car door for prints. Think of how many things you touch in public every day. People will be harvesting public places for prints and compiling massive lists for cracking if this is ever used as a method of online security, and since Apple are a bunch of idiots Apple account log in via fingerprint will probably be a launch feature.
Yeah the idea is silly, its also not new, its been done before long ago (although it failed then) so i suspect this will probably fail too.
Im yet to see a finger print reader that cant be fooled by using latex gloves or selotape (domestically available) . Even top end finger print devices have the same floors and they have stuff like heat detection and circulation detectors built in.
Your view may come across as paranoid but with all the stuff going on it's not a far stretch to imagine your finger print data being logged without your knowledge.
i had a laptop with a fingerprint reader, and i loved it, i'm not too concerned with security 90% of the time, it's great for never having to remember passwords
i don't see people dusting for prints and stealing your phone just to post asinine comments as you on facebook, people who use this on important passwords for bank accounts an the like would be retarded, common sense should tell you that it makes things less secure, not more
I think it would be more secure than a 4 digit pin.
I had an HP laptop with a scanner, and it made logging into the laptop, and websites easy.
as far as "Government spy oh god dskfjskljfsfs"
If the government wants to find you, they will. If they want your bank account info. they already have it. You name is already tied to your phone via a cell company or credit/debit card, they already own you.
Don't forget that there's a Motorola Droid with this already, except that you have to swipe, in fact, I bet this technology on the 5s is pretty much the same as the traditional swipe scanner. You criticise it but you're criticising on a piece of technology that's pretty widely used around the world today and then.
EDIT: BTW, here's another earlier thread on this: https://teksyndicate.com/forum/phones/new-iphone-5s-features/152705