Do Free Samples Work?

I wonder how much of the purchasing done after trying a sample is done by "guilt" - as in trying a product and feeling bad about not buying it...

"Product samples work, according to a study by the research firm Arbitron. More than a third of people (35%) who accept a sample in a store or a mall go on to buy the product that day, the study found. And 58 percent who sampled products said they would buy them in the future. Samples are more effective among people who have not previously heard of the product, Arbitron found. Roughly two-thirds (64%) of people accept samples."

-NYTimes, October 6, 2008