Companies who purchase a promoted trend get a customized hashtag placed at the top of the list of trending topics. Users who click on this hashtag see a tweet from that company at the top of the page of results. Big brands like Coke, Disney and Hyundai have purchased promoted trends over the years and so did both the Obama and Romney campaigns during the 2012 presidential election.
Twitter has increased how much they charge companies to buy a “promoted” trend in the from $80,000 back in 2010 to $200,000. I don’t use twitter that often so I wouldn’t know off hand how an ad like that would influence me but I feel that $200,000 is a large amount to pay just to promote your company on one social media site out of many.