Mr Blumenthall has popularised the use of liquid nitrogen amongst chefs and catering establishment – but it really, really is dangerous. Aside from the cold burns from handling its the rate at which it expands when it warms – its something in there region of 700 times more volumnous at room temp than when its liquid – so just having the lid on the container too tight (or having the lid freeze on) and you create a bomb. There was a german chef who blew both his hands off when a flask went off and theres an account somewhere of a flask of it exploding in a school/college and the number of floors flask smashed through before it came to a rest. So the risks go beyond those to people decanting or drinking it – the venue effectively has a bomb in it.
In the flask it looks pretty harmless but just something simple like sticking a straw or tube into the liquid can cause it boil in the straw and jet a fountain liquid nitrogen out.
All that said…. there was nothing to stop me buying 45 litres of the stuff earlier in the summer, and although the supplier was very helpful and gave plenty of instruction on safe handling and storage there was nothing that required him to give that advice and nothing prevent me or any other idiot buying it with or without those warnings, or to stop them re-suppling it again.
I did have a near miss with the lid on one flask I was decanting freezing on, theres a split second where you hear/feel it grab and you have to decide whether to try and wrestle it off or run away – I just had to lob it into the woods and hope it didn’t go off.