And thy Shall Not Steal!!!

Answer the individual questions and connect them to a single entity...

1."Our mission is to enable users to search complex fields on the Web intelligently. We're starting with health and medicine – an area where many people will appreciate a service that helps them quickly get high value information, and a field where we have expertise based on our work with health-related organizations."
Which company am I talking about?

2.X is a company based in San Francisco, California that is developing a natural language search engine for the Internet.

X is working on building a natural language search engine that can find targeted answers to user questions (as opposed to keyword based search). For example, when confronted with a question like "Which U.S. state has the highest income tax?", conventional search engines ignore the question phrasing and instead do a search on the keywords "state", "highest", "income", and "tax". X on the other hand, attempts to use natural language processing to understand the nature of the question and return pages containing the answer.

3.X was a reverse auction online shopping site website.It is the first website exclusively using "cost per action" for shopping, and the first to give ad revenues to customers, by means of rebates on purchases.
What's X.

4.X was Founded in 2003 by Oren Etzioni (founder of MetaCrawler and a professor in the Department of Computer Science & Engineering at the University of Washington), and has collected over 175 billion airfare observations to date. X's team of data miners use these airfare observations to build algorithms to predict future airfare price movements.
Identify X.

5.X was created in 2006 by Jack Dorsey. Since then it has gained notability and popularity worldwide. It is sometimes described as the "SMS of the Internet" since the use of its application programming interface for sending and receiving short text messages by other applications often eclipses its direct use.
Identify X.