PY – “The only problem with that is that people see animals in operation all the time and know they can be ferocious. Nobody that I know has ever seen a sheid, or even described what harmful things they do, or how they go about doing those things. Nobody has ever even given an example of any damage that we could not explain through purely physical means, such that we would have to look for some other cause.”
I believe most shitos hold that sheidim are no longer around today. The explanation I heard for this was that when the koach ha’tahorah (navim, open neisim, etc) was diminshed, the koach ha’tumah (sheidim, kishuf, etc) was similarly diminished to keep things balanced.