But I'm afraid I have no sympathy for outraged users. No more than if it was gmail or hotmail. They didn't pay for the service, they got an email service for free. It's hard to complain when it is free. And they did enter into an agreement where they sell their privacy against a free service.
I'm sure you are right that it is a low percentage, but I bet there are a lot. When I used Yahoo, I paid, as did my wife. For the extra storage, no ads, and I could be misremembering, but I think paying got you access to imap or pop3, which wasn't generally available before the iPhone.