This sort of goes along with the last post about being mistaken for your protagonist. That would be fictionalizing yourself. But what about fictionalizing other people, or having other people mistake themselves for fictional characters based on small details you’ve procured from them to use in a story? This has happened to me with my first book. Michelle Huneven covers all the bases on this topic in The Paris Review blog.
The title of your post caught my eye. The current novel I’m working on is a fictional story based loosely off my life and personal experience. Certain names and details have been altered by the core of the story remains.