Not really sure I see there's a problem personally. It doesn't look like any of the lads are being co-erced into taking part and, truth be told, they look reasonably adept at controlling their entry profile (OK, with one exception). The tree is not that more dangerous than the dome (the fact that it moves whereas the dome doesn't is more of an issue than the increased height). OK there are injuries, slight in this case, and I accept there are iolated cases of illness from playing in the river (but I understand it's a lot cleaner than it used to be) but I'd prefer the lads kept their sense of adenture and adrenaline alive than fester on the street corner, drinking cheap booze and swearing at passers by.
Now where are my board shorts :-)
RH