NDE is short for Near Death Experience. This is where someone goes unconscious, becomes clinically dead, sees some sort of vision, and is then revived to tell the tale.
Here's why they're bunk.
1) When does an NDE take place?
Did you have a dream last night? Do you know when it occured? Most people who said yes to the first would answer no to the second unless they actually looked to see what time it was (by a clock / seeing the sun or moon / etc).
Those arguing in favor of NDE's always overlook the fact that NO ONE has ever gone from being completely conscious to having an NDE and back to complete consciousness. Most individuals who experience them are in hospitals, not in their right minds and slip out of consciousness... sometimes for hours.
So, to believe all this, you must accept that individuals develop some magical sixth sense that allows them to tell when their experiences take place... an ability they lack while healthy, but which they miraculously gain while DEAD.
"Nope. It couldn't have been a dream while I was asleep after they got done bringing me back. I know I saw teh god while I was dead. Because... I say so!"
2) Rare occurances.
I have no doubt that there are individuals who see something when they go under (probably while they're unconscious, but still very much alive), but for every person that has an NDE, there are hundreds or even thousands who do not. They are rare occurances and even under near identical conditions some individuals never report having them.
I'm also sure there are a number of people who claim to have them to gain attention.
3) They prove nothing.
You went clinically dead and came back. Your brain worked before. Your brain works after. Even if you flatline, it's far more likely that your brain was semi-working while you were under... (Remember that many hospitals don't attach brain wave monitors to trauma patients.) ... than something mystical happened to a non-existant "soul" you've convinced yourself you have.
If we wanted to, we could spend days imagining supernatural elements for every aspect of our bodies.
NDE's just evidence that we don't know everything about the brain. Calling them anything beyond hallucinations is just a form of god-of-gaps reasoning.