Twitter may be amazingly popular, but it’s had major trouble turning a profit. So that’s why it has a new CEO. Co-founder Evan Williams has stepped down after 2 years running the company and will be replaced by the company’s chief operating officer, Dick Costolo. Costolo, 47, may be a better fit within the tech community than Williams who is staying to focus on product strategy. Costolo. He founded RSS service FeedBurner which he sold to Google in 2007 for $100 million. HeW said today in a statement, “We have awesome stuff in the pipeline, and we’re ready to accomplish more in the next two years than we’ve accomplished in the last four.” But can Twitter monetize its cool factor? Well, the company is next venturing into targeted ads that “find” users based on the words in their tweets.