Startups are leading the way in Big Data, even managing to grab the attention of the industry’s largest and most profitable companies.

On Monday, Apple confirmed that it picked up Topsy in a deal said to be worth more than $200 million. The San Francisco-based social analytics provider is one of only three firms with full access to the Twitter firehose, a real time data stream that averages around 500 million tweets per day. Its technology is used by top media companies to gain insight into consumer sentiment and measure the success of their marketing campaigns, among other things. Apple wouldn’t say what it bought the startup for, but analysts speculate that Topsy’s software will be integrated into Siri to deliver more personalized search results. The consumer electronics giant could also leverage the technology to make iAd and iTunes more attractive for partners seeking to gain greater visibility into their audiences.

DataSift, another company with access to the firehose, raised $42 million in Series C financing to break into new markets and expand its platform. Unlike Topsy, which focuses exclusively on Twitter, the firm covers a broad spectrum of social interactions that extends encompasses Facebook, LinkedIn and dozens of other sites.

Over in the real time analytics space, Nurego received $2 million from Accel Partners for its cloud-based opex optimization solution. The stealth startup, which includes former VMware CEO Paul Maritz on its board, says that the service features “patent-pending technology [that] combines the power of big data and sophisticated subscriber-centric workflows to help cloud service companies build a metrics-driven business.”

Finally, spinoff startup Trufa bagged $4.5 million in funding to accelerate the development of its ERP analytics software, which enables users to quantify the impact of business decisions on the bottom line.