Bandwagon effects are hard to prove.  If an artist is popular, does that popularity by itself draw others in?  Are you more likely to enjoy a movie, restaurant, blog just because you know that lots of other people like it to?  It’s usually impossible to distinguish that theory from the simpler hypothesis:  the reason it was popular in the first place was that it was good and that’s why you are going to like it too.

Here’s an experiment that would isolate bandwagon effects.  Look at the Facebook like button below this post.  I could secretly randomly manipulate the number that appears on your screen and then correlate your propensity to “like” with the number that you have seen.  The bandwagon hypothesis would be that the larger number of likes you see increases your likeitude.