[vidarh]

It does sometimes improve security for the user.

This happens when the auto-complete triggers on things it shouldn't and the user doesn't notice and submits personal details they never wanted to send to the site at all.

I've had to struggle a lot with working around Google's wrong-headed approach to this because this actually happens to real users. It's downright irresponsible, and I think frankly it's just a question of time before EU data protection watchdogs starts to take notice. All it will take is a sufficiently bad case of unintended disclosure of personal information (e.g. imagine a domestic abuse victim accidentally having their new address auto-completed in just the wrong situation).

(EDIT: this also easily happens with web apps where someone has to enter details for different users in the same forms multiple times; it get's very easy to end up not noticing Chrome auto-completing details for unrelated users; if that information is later visible to the user, it creates a real risk of leaking personal information)