Earlier I theorized that after a web service you find useful becomes "social, and a lot more fun", it becomes something that you might, occasionally, find useful.
In the case of Prismatic, this seems to have borne itself out. It went from providing interesting links to pushing clickbait. I can't be bothered to try and train it any more. Maybe I'm a curmudgeon? I may have to adjust my theory to take that into account.
My kingdom for an editor.