Could this be dialectal? Because I hear "ni" now and then, and I've also found myself using it a couple of times -- not through intent, but rather automatically. Maybe it's the "new trend" you're talking about.
Maybe it's a central Stockholm thing, I don't really know. And I certainly didn't mean to imply that it was common, I only noticed it now and then and vaguely recall some mention of it on P1 Språket or in the newspaper, that it seemed to be making a return.
I've only ever known du, would never use ni except for a group, and feel odd being called ni myself. Not insulted mind you, closest I can describe it is like when a small child refers to you as "that man" but you're only 16 or 17. :)
