Its kinda like asking an ice climber how many anchors they use in a hanging belay.
Ummm... not quite... *if* you read my clipped comment in the context with the rest of the post.
*If* one is actually scuba diving... then obviously the "each diver has their own tank" thing goes way beyond just a good idea... however...*if* this is a purpose shot video in shallow water for the purpose of showing off/getting people talking/creating controversy... (think hollywood stunt men doing a rigged demonstration where reality does not apply)... then "just perhaps" one tank *is* enough...
... as I said in the post and as kadleck pointed out... THERE ISN'T ENOUGH INFORMATION in the video to really know what is going on.
But, it all goes to how one chooses to percieve the visual clues that are scattered throughout the video... a big 'clue' for me is the very ending... I doubt that most on this board could sit happily on the bottom with a wetsuit and weights... go through the drills this kid did... and then happily swim away (note the lack of use of arms... really nice bouyancy control off the bottom... and that nifty little mask clear in mid-swim the kid did)... with the kind of ease and control the kid did... This kid isn't being "taught" anything... my guess is he probably spends more time in/under water in a week than most of us do in a month...
I don't know what all was going on... but I'm pretty darned certain that this kid has done this all before... there is no "lesson" going on here... regardless of what the 'title' of the video is... and any 'risk' lies in the perception of the viewer...
... now, that being said, does it create a scenario that might encourage somebody go out and emulate them? Possibly... on the same level/scale that television commercials/video games/movies, etc. do. (Ever watch "X-Games"... "Jackass"... almost ANYTHING 'extreme' that's geared to teens??? Way excessive... makes this look like Nader safety video...)
Watching a video isn't going *make* people do dangerous things... being an idiot will. The video may, at most, provide ideas that the less than creative idiot might not have thought of... but it doesn't increase the probability that the idiot will... in time, do something terminally harmful to themselves... or others.