Wiktionary
n. (context Internet English) An internet site that deals in information pertaining both to businesses offering goods and services as well as potential customers.
Wikipedia
An infomediary works as a personal agent on behalf of consumers to help them take control over information gathered about them for use by marketers and advertisers. The concept of the infomediary was first suggested by former McKinsey consultant John Hagel III and former Harvard Business School professor Jeffrey Rayport in their article The Coming Battle for Customer Information. It also appeared in the book Net Worth.
Infomediaries operate on the assumption that personal information is the property of the individual described, not necessarily the property of the one who gathers it. The infomediary business model recognizes that there is value in this personal data and the infomediary seeks to act as a trusted agent, providing the opportunity and means for clients to monetize and profit from their own information profiles.
One of the first focused implementations of the infomediary concept was an online advertising company called AllAdvantage launched in 1999. While that company did not survive, in more recent years there has been renewed interest in the infomediary concept, with entrepreneurs and investors building companies to identify and leverage the market value of consumers' information.