Many people job-hop because they are fleeing difficult peers or, more often, difficult bosses. They're hoping, of course, that they will get to work with more amiable peers or bosses in their new situations.
According to the United States Department of Labor, young people entering the workforce today are likely to change jobs seven to ten times in their careers. Although people move for many reasons - to seek better compensation and opportunity, to move to another part of the country, or because their jobs are outsourced - many people change jobs to get away from difficult people. What they find in their next job is more difficult people. And so they continue hopping from job to job in search of the utopian workplace.
Unfortunately, difficult people are everywhere. In today's workplace, you just have to learn to get along with them to succeed.