Simple experiment. Make a website with 3 buttons, and invite 10K people to visit. Make strong assurances of anonymity: and independent 3rd party will select the participants, logs will be destroyed, etc:

* Bill my credit card $20, donate to a pool to send to http://www.againstmalaria.com or somesuch. * Spend $20 of the researchers' money on fresh vegetables, and throw them in the trash. * Do nothing.