An interesting article on social herding behavior in voting patterns with impact on QAs sites like BioStar has just come out in Science:
Lev Muchnik, Sinan Aral, and Sean J. Taylor, Social Influence Bias: A Randomized Experiment, Science 9 August 2013: 341 (6146), 647-651. [DOI:10.1126/science.1240466], http://www.sciencemag.org/content/341/6146/647
Quote from the abstract:
Whereas negative social influence inspired users to correct manipulated ratings, positive social influence increased the likelihood of positive ratings by 32% and created accumulating positive herding that increased final ratings by 25% on average. This positive herding was topic-dependent and affected by whether individuals were viewing the opinions of friends or enemies.
Herding effects were topic dependent.
The authors showed significant positive herding effects exists for topics like "politics", "culture and society", and "business". No significant impact was shown for e.g. "IT" (I am so relieved ;)), "economics", and "news". They observed a general trend to "correct" negative votes by up-votes. No negative herding effect was observed.
I have seen situations (on stack exchange type sites) where someone with a very high score makes a trivial comment saying they agree with somebody else's comment, and the high-ranked individual gets upvotes for this, even when the person who made the original comment does not.