"...100 of his vocal supporters can dictate the stories for a site with 100,000 users."

Only for as long as the 100,000 is reasonably happy with what the 100 is providing them. Otherwise you'd think they'd have the sense to either start downvoting, or simply stop using reddit, rendering it a site with 100 readers who all vote. More likely many of the 100,000 see reddit as their best source for all the Ron Paul news the 'mainstream' media is 'trying to hide' from them.