Microsoft wants to combine this data with information collected as people conduct searches with Bing and surf the Web with Internet Explorer. Using that data, the system will build an emotional profile of a user that will enable it to deliver ads "with the highest monetization values to the users that are emotionally compatible," according to the patent application.

Microsoft's plans are merely at the patent application stage. Other major companies are much closer to implementing emotion-sensing technology.

, a company whose software can scan a photograph and identify who's in it, based on user tagging.

While much of the press coverage of this acquisition has focused on the potential threat to privacy posed by facial recognition tools, a lesser-known feature of Face.com technology is the ability to detect emotion -- with stunning accuracy.