How many of these people were being handed a survey and decided to be sarcastic, and are sitting there going "hmmm, amazingly these idiots took the results seriously".
That said some of this is ambigious.
For example, memory erasing technology DOES exist, it's not so much a matter of technology as much as our understanding of technology. Hypnosis, brainwashing, deprogramming, it's all real. People tend to forget that there are hynotists who put on shows where they will pick a guy out of the crowd, make them bark like a dog or whatever, and then forget the whole experience. Some of you might have even had it done to you. As a result saying "this doesn't exist" and that the people are misinformed there is wrong.
Lightsabers, okay those we don't have yet.
Teleportation technology, well that one is ambigious, there are a lot of believers there. Everyone knows all about how the US faked "The Philedelphia Experiment" or whatever to freak our enemies out, and we really didn't make a ship disappear for a few seconds.
What a lot of people don't realize is that the motivation for this goes back to research on "Psychotronic Weapons" during World War II. Hitler was up to all kinds of wierd stuff. Despite what the name sounds like, "Psychotronic Weapons" were a teleportation based delivery system where the idea was that they wanted to deliver bombs to targets without having to drop them from planes. There are rumors that they managed to transport a grapefruit like 11' but it imploded. The research continued after that point and was tossed around by various nazi scientists and their successors afterwards. There have been a few bits of posturing back and forth with differant countries planting information trying to show how close they came to freak people out. I'd guess it's become sort of the espianage version of a bad joke nowadays. HOWEVER there are always those persistant rumors that someone managed to do it on a limited scale and pointing towards little things here and there a examples where the tech might have been used. It's conspiricy theory material, and something people who follow wierd military research and read up on World War II and stuff have probvably come accross. It's funny because I think "Dragon Magazine" actually made some mentions of it in one of their articles as a way of pointing out how wierd things that have happened can inspire RPG ideas. The point here is that there are probably a lot of people who DO believe we have teleportation technology somwhere, I doubt anyone believes there are Star Trek teleporters (it would have changed too much) but there are probably people who think that there is a goverment lab where they can teleport rats four feet or something. It's not proven, and unlikely, but it's not THAT insane either.... on the level of your typical conspiricy theory.
When it comes to hover boards, I'd actually be shocked if there isn't a prototype that fits that description somwehre to be honest. I say this because during the promotion for the movie "Robocop 3" years ago, they had a guy with a Jet Pack flying back and forth outside a movie theater where it premiered. The Jet Pack was nothing like the one in the movie, or what you see in video games, but it was an interesting oddity. They have probably gotten better since then, I haven't followed it too closely. I have never *seen* a hover board, so I would never say "yeah they exist for sure" they are definatly not a consumer item, but from what I've seen of Jet Packs I wouldn't put it past some bozo to put a device like that under a surf board or something and try and see if he could lift himself up on one and control it. Somewhere out there, there is probably a hover board in the garage of some science nerd on the level of the guy who The Escapist ran an article about who made a functional low-end laser pistol.
I guess the point is that while I think this sounds like a lot of people looking at this and deciding to be sarcastic (seperatly, not coordinated), on SOME of these cases, I don't think the answers are quite as insane as they might sound. What's more with all the wierd things people have shown off on TV that some guy invented and got a short bit of screen time to demonstrate (and were never seen again, at least by me), I'm reluctant to dismiss much of anything since people have made some really WIERD crap that I would have thought was impossible over the years. In a situation like this it would probably be more accurate to ask not "is this commonly availible" instead of "does this exist", because as I said, you'd be surprised at what some bored people have cooked up in their garages and shown off on TV at various points. I don't think lightsabers exist (as explained above) but if some dude in New Jersey came out and said "hey I came up with a way of generating a laser blade that can last for 14 seconds using the diamond from my ex-wife's ring as the focus" and then demonstrated it on TV... I probably wouldn't be all that shocked either, because over the years I've seen stuff that has literally been that insane seeming.