DZoH and I were away this weekend. When we got home this afternoon and I came online, everything was fine. I was Zombie. I stay permanently logged in, btw. Then I noticed that some of my Customised settings appeared to have changed. I changed them back to my usual settings. A bit later I clicked on Threads I'm On and the threads weren't mine. I clicked on one and scrolled down. Another poster's posts were highlighted (not the OP) and when I got down to the Message Box, that other poster's name appeared beside Nickname.
I clicked on InBox and it was their PMs. I didn't look at any of those. It appears that somehow my registration was temporarily tied up to their account.
Blimey . I want the science. How could that happen? Could it in theory happen on any other site where what you see is dependant on a straightforward login/password? Is that why banks throw in the PIN as well for online stuff?
I don't know how it happened but I think Joyful is right and it has happened before. Whether the poster I became also became me or whether it was more random than that I also couldn't say.
I have PM'd the other poster whose identity I temporarily assumed to let her know what happened and to warn her that I may well have changed some of her customised settings before I noticed the nickname change.
But it's the combination of the three things that tells MegaBank that yes, this is definitely Hassled. The unique identifier isn't, on its own, enough. On MN (and Amazon and Ebay and loads of sites) the only thing telling them that this is definitely Hassled is the Username/password combo.
But I still don't understand at all how this happened to Zombie. It's all a bit Twilight Zone.