Erin stole my identity. She was updating her Google profile information and posted a picture to the Web through Picasa, which happens to log in as me. That changed who was logged in, but not what information was displayed on the page. Then she saved her updated profile, and all of the information from the page saved as mine. Now I've got the task of fixing my profile to be me again.
At least we know this kind of crazy thing can happen, but it does show one of the limitations of web applications.