WisdomTap (www.wisdomtap.com) is a firm that uses purchase intention in a very interesting manner.
They spot purchase intention in public posts and target advertisements at the speakers.
The team at WisdomTap obtained some startling results when they measured how those users responded to their ads.
The results can be found in this whitepaper: http://www.aiaioo.com/whitepapers/intention_analysis_use_cases.pdf
Aiaioo Labs Blog 