http://www.worldjumpday.org/
It's hilarious that people think this would actualy work, anyone over the age of 13 could surely figure out for themself that it just wouldnt work for so many reason. I can't even be bothered to start going into the millions of reasons why this wouldnt work.
I guess in a sense it poses the same question as 'If a lorry full of birds breaks suddenly causing every bird the instantaneously fly from it's perch, does the lorry wiegh more or less?' When in fact, the lorry wieghs exactly the same, nothing will happen, you'll just get a bunch of morons jumping up and down