Interviewers are concerned about job hoppers people who do not settle but move from job to job. In a recession many jobs are short-term and so this may not be a negative reflection on you but the interviewer needs to be convinced.

If you have changed jobs more frequently than average, be ready to explain the reasons why. If it is a case of a job not working out, be ready to explain. It could be that you moved for a promotion but within weeks you realized the company was in difficulty, with your job at risk, hence now looking for a new job.