Edward Tenner points to an old Princeton study (from May of last year):
Researchers enlisted more than 12,000 volunteers to rate and download songs from among 48 chosen for their relative obscurity. Some of these volunteers were lied to: At a certain stage in the experiment, popularity rankings for this group were reversed, so the least-downloaded songs were made to appear most-downloaded. Suddenly, everything changed. The prior No. 1 began making a comeback on the new top dog, but the former No. 47 maintained its comfortable lead on the old No. 2, buoyed by its apparent popularity. Overall, the study showed that popularity is both unstable and malleable.