Mundane thought: I don’t recall seeing the amount of hopping at major US sporting events that I see at World Cup. Seems common among soccer fans worldwide. The US soccer fans being shown at World Cup are hopping as good as the other fans.
Do you think this hopping will catch-on for NFL, NBA, NHL, or MLB games? I am not sure why, but I don’t think it will - maybe it has to do with the facilities? I don’t know. Thoughts?
It reminds me of the way my 4-year-old son acts when he’s excited.
Hey, at least those infernal vuvuzelas are gone now.
I respect the energy expressing efficiency of these hoppers. When people are really crowded together, pogo-ing up and down sounds like a good bang for the buck. I wonder if any of the fans who make incidental side to side contact with each other then flop and scream like a true soccer pro.
Jumping in unison on some bleachers that were slapped together at the last hour in Brasil is probably not the smartest thing to do.
Restroom facilities at the new stadia were a victim of budget cuts.
It can be fun to do and goes with certain cheers. It looks very cool from the right angle, too. First saw this at an end of season Borussia Moenchengladbach match some years back.
It can, also be hell on your old guy calves, he came to learn. 
And in some venues it does make me nervous. At Everbank Field in Jacksonville during the USA v Nigeria match a few weeks back, you could feel the stands rocking beneath you, even though they are not just bleachers slapped together.
My additional though is that US interest in soccer is reaching another peak after another long drought. US soccer fans are learning from more seasoned soccer fans how to cheer and celebrate the game, as is customary in other countries. ISTM our fans for traditional US sports are either more reserved, or choose to cheer in a different, more individual way. It would be kinda fun to see all the mutant Oakland Raiders-type fans cheering at World Cup - I don’t think they’d be hopping, tho.
Moving this to the Game Room from MPSIMS.
It intensifies the support you give your team; as an example:
Here’s the Lech Poznan fans literally shaking the stadium
Red Star Belgrade prefer to bring along flares and fireworks
It’s also very common in NCAA basketball games. I first noticed Duke fans doing it around 10 years ago or so.
Camp Randall in Wisconsin has had jump arounds between the third and fourth quarters for decades now.
I first saw a team do this at the '99 world junior hockey championships in Winnipeg. Not something you expect to see on a sheet of ice.