Basically when you throw in the pound sign, when you're on twitter it becomes a link to a search for that term. If you click on the #OOTPX you get taken to a real time search of the people that tweeted about OOTPX If you just type OOTPX there's no link to it. So in efforts to garner attention to my league in the OOTP world, I've been using that tag (I'm cbu_ootp) to help start a trend. I don't think we'll ever get to the top 10, but if you ever did, it'd be huge huge huge as millions would click to figure it out what is being talked about.
So that's why certain companies have run contests if you mention their companies keyword. Because if they reach the trending topics the social media world sees it. But if you can get a deal with Ashton Kutcher to endorse it, you'll get tons of attention