I went last week for 8 days and purposely did not try to hide my Sony Action Cam (it looks like a Go Pro only a bit more compact). It does not have an LED screen and it's super tiny. It's not on a selfie stick but does have a "handle" that is the length of my palm and does not extend. When I went on rides I made sure it was clearly visible to test if they were going to say something because I was curious. The only ride any cast member said something to me on, ironically, was living with the land. I had it laying flat in my lap and it was not turned on. She yelled at me (in a not so nice way) to not hold it up during the ride. I just nodded at her and that seemed to make her even angrier and she repeated herself. At this point I was irritated - again it wasn't on and was laying flat - so I said "I don't hold it up in other people's way" and she seemed miffed but let it go. She never asked me to put it up so I don't know what she was wanting from me exactly. It wasn't a magical experience.

It wasn't what she was saying but how she said it.
The reason I found that ironic is no one said a thing to me on any of the roller coasters or rides where they could be more problematic. Mine has a wrist strap and I keep it in front of my body as to not bother others so there's no danger to anyone or annoyance, but I can see how Disney would want to err on the side of caution. I have pivothead glasses so it's not a big deal to me if I can't hold the sony camera but I prefer using it - better picture, more stabilization.
Also, a friend of mine just this past weekend rode Primeval Whirl with his goPro clearly visible and the cast member said nothing. He rode it again 10 minutes later and they made him put it away. As usual seems to depend on the cast member and there seems to be a lot of confusion over what a selfie stick is.