The largest IPO was Twitter (TWTR), the California-based social media platform, which raised $2.1 billion last November, leading the tech-based IPO offerings for the year. While the consumer Internet IPOs may have grabbed the most attention, the M&A market remained sharp and focused, with several companies topping the $1 billion price point. Salesforce.com’s $2.6 billion acquisition of ExactTarget was the biggest M&A dealing 2013.