The only time I have personally witnessed someone injured by liquid nitrogen (And the amount of LN2 I have personally worked with is in the 1000's of gallons) was in a undergraduate lab course at UT Austin.

We had finished our labs and had leftover LN2 - rather than waste it we proceeded to play with it- freezing things, pouring it on the floor to collect the dust and create swarms of fast moving dust bunnies. I was having fun quickly scooping up handfuls of LN2 and throwing it...

We took an empty diet pepsi can and filled it with the LN2- water and CO2 from the air formed frost on the can, liquid oxygen formed small droplets on the side of the can- we were marvelling at how it was the epitome of 'cold'....

Someone brought up the classic movie 'A Christmas Story' in which a group of kids dare a poor child to stick his tounge to a flagpole in winter- A student from the UK had never seen the movie and so we explained the scene to him- how the schoolyard episode progressed to the dreaded "double-dog dare" thereby forcing the poor kid to stick his tounge to the flagpole- he thought it was funny... someone (I refuse to name names) jokingly said 'I double dog dare you to stick your tounge to that can'- it was just a joke, there was no seriousness in it... The dare was offered to the UK student, who had made a constant point of demonstrating that - while he may be a physics major, he was a mans man-

The student from the UK goodnaturedly said OK! and leaned down to the can- we laughed, just thinking he was joking around, playing along... he stuck out his tounge- we kept laughing... thinking 'wow his tounge is awfully close to that can, just like him to push it to the edge....'

And then he touched his tounge to the can- the laughing stopped and there was a gasp.... I dont know if he did it by accident, or mental defect.... we stared in horror as he tried to pull back from the can and only succeeded in dragging it along the desk. He started trying to articulate his distress but all he uttered were inarticulate grunts- he started to panic and stood up- the can followed, dangling from his tounge- the fear was clear in everyones eyes, especially his... he tossed his head violently trying to get the can to release its icy deathgrip on the tip of his tounge- LN2 spilled from the can, but it stuck fast.

He then made another in a long string of mistakes and tried to pull his tounge into his mouth- the can immediately froze to his lips.... I remember the high pitched incoherent muffled scream he gave- he stared wide eyed at us- as if pleading us to help him, it was to no avail... our shocked brains were still trying to process the fact that he had actually gone and done it! In any case how could we be expected to come up with a solution to this unusual real-life physics problem in a split second?

FINALLY he reached up and pried the can away fom his mouth... knocking it violently to the ground and ran out the door to the mens room down the hall...

I don't know how long the silence lasted... someone finally said 'Did he really just do that?!' we broke into nervous laughter and one of us went to the bathroom to make sure he was ok....

About 5 minutes later he came back with a wad of paper towels dabbing at the flowing blood from his lips and tounge- we asked if he was ok or needed to to the medical center- "No...." he clumsily replied while occasionally pinching the tip of his tounge with the paper towels "Its ok... no worse than eating a hot pizza... really"

And so he became a legend...