Has anyone ever seen a pokestop/gym removed?

Yes unfortunately, and for no reasons, they removed a gym in my hometown.
They transformed an existing pokestop into a gym, but that is located in a very dangerous place: in the middle of a high speed statal street.
Nonsense.

Yes.

My first silver badge gym got removed in July.

Yes! They removed a gym and stop from behind my house when that land was turned into a school. There was also a local rec center that requested there's be taken away for traffic reasons.

I noticed two stops disappeared in my area several month ago. More recently, 10 have been added and I guess about 8 stops became gyms.

Niantic states it was the backlog of requests from last year. Funny, the playground equipment in the photo disc image is only a month old.

In The Netherlands they removed gyms from train stations like half a year ago.

Yeah. One was on private property.

I saw a pokestop removed from right near a high school in my town. There are no spawns or pokestops near the schools in our town.

Yes. Lost a Pokestop due to a Boost mobile closing.

We have a gym at a water tower that was only accessible by either stepping a few feet off the walking trail next to it or by parking in the parking lot of the daycare/preschool next to it. The daycare happened to be a pokestop as well. I avoided both during operational hours.

The gym was relatively rarely used pre update, but then there was a tyranitar raid in the afternoon one day. The cops were called and the group was broken up. Less than 3 days later, the pokestop was removed and the gym was moved so that it is now more easily accessible from the trail. And now all local players know to park and walk to that gym.

A Pokestop was removed just 50 metres from my house, but a new stop was added 10 metres away, and another existing stop right next to it changed into a gym.

We lost I believe 17 Pokestops and 2 gyms in a single area (1 block radius) a little bit after the Halloween event.

Yes, I've seen a gym removed. It was a duplicated ingress portal. They removed one of the portals which was named exactly the same and pointing to the same monument.
The gym removed was placed on a different portal a few meters away from the original one, though

Yup. Of course the stop removed was the one I could access from where I sit at work. I noticed a new stop added near my work just two days ago, so it seems to be a fluid process.

Yes, I had a gym and two pokestops near my house removed just after the gym revamp in June.

This was the closest gym to me, so was a bit annoying to lose.

The gym an one of the pokestops was at a school, while the second pokestop was at a neighbouring school. I guess that the school authorities had lodged a complaint.