Several security experts said they had not heard of a case like this, in which the wrong person was shown a Web page whose user name and password had been entered by someone else. It's not clear whether such episodes are rare or simply not reported. But experts said such flaws could occur on e-mail services, for instance, and that something similar could happen on a PC, not just a phone.
All examples given are from AT&T users, and the company says it's working on the problem. I'm having trouble seeing how it could happen on a secured connection to a PC. What the cell networks do with Internet data is another matter.