[brunolazzaro]

Well, the bug seems NOT to be on the ammount of fields, or that they are hidden.

But that they all have the same name="" in them. Probably causing Mobile Safari to loop trough all of them (at the same time?) for some reason.

Here is the same, but without the fields hidden, and without name attributes: http://jsbin.com/EziLODur

I just tested it on ios7, on a 4S and while there was a 2-4 second lag on the initial tap, after that it worked fine on every field.