Closinglogos.com is a site dedicated to this phenomenon.
They have also now made a documentary about it. Trigger warning – do not watch if you find these scary.
And a commentary about it.
My own story about this is that I was not afraid of these logos (surprisingly – as I was afraid of some weird things, like the brassy build up in this Otis Redding song – and I loved Otis Redding).
BUT I once had a nightmare about the old NET logo: that I tried covering my eyes from it and I still saw it. It didn’t scare me otherwise.