Full disclosure: I kinda respect the legit downhill longboarders. The ones who do powerslides and rock slider gloves and break 60 mph are a very different breed than the hungover frat bro in flip flops pushing across campus on his Santa Cruz longboard.
But yeah, downhill contests are rad and gnarly on real skateboards too. Snack did a couple on Dolores in SF and Roughneck hardware had one on the back 9 hill route about a decade ago