More sampling means more buying, at least according to Last.fm cofounder Martin Siskel.  Just recently, Last.fm started offering full-length, on-demand previews on a considerable catalog, instead of 30-second samples.  That has now caused a "direct and positive impact," specifically a 119 percent gain since January.  "In just over two months it's become clear that people will buy CDs and downloads if they get access to the kind of service we offer," Siskel said. 

Siskel pointed to a potent combination of previewing, discovery, recommendation, and social networking, elements blended smartly by Last.fm.  Specifically, Siskel referenced an Amazon-based increase, though the company also has affiliate partnerships with iTunes and 7digital.  But the specifics ended there, and the company declined to detail hard numbers.  That raises questions about the absolute volumes involved, and introduces the possibility of insignificant totals.

Last.fm parent CBS also outlined related increases in February.