It's just too easy to screw that up and despite the argument proferred there is no real benefit. If typing on mobile devices is hard it doesn't seem what we need to do is post our credit card numbers online.
I used to work as phone support for a webapp targeted at Real Estate Agents. 60% of our web + phone support requests were related to passwords. A third of those requests were errors due to misspellings.
An option to reveal the text of the password field would have a drastic effect on these support requests. It would lower calls and call times on these issues. Even if this 15-minute change only saved 30 minutes of support time a -year- this would be a net win.
You might not screw up passwords, but plenty of people do. I'm not suggesting to have it permanently visible, just the option to make it visible. This enables people with password issues to debug their own issues before resorting to a password reset or contacting support.
