Group Interviews Hurt More Than Help
A group interview is a process in which an employer calls in a group of potential employees and makes them interview for a position in front of one another. A group interview should not be confused with a panel interview, where one candidate interviews in front of several interviewers.
Proponents of group interviews think they're just dandy because they allow the interviewer to 'see how candidates interact with other people.' Unfortunately, this is not what happens with group interviews, what actually happens in group interviews is that the interviewer gets to see 'how candidates interact with other people who want the same job they do'. It's Survivor: Unemployment edition and it's a patently insane way to try to hire for a position you actually care about.
One could argue that if you don't have time to interview to fill a position, then you don't have time to fill that position properly. It's no wonder that positions filled by 'group interview' often become vacant very quickly. If someone is mad hatted enough to assume that putting a prospective employee in a tense and inherently unpleasant social situation is a good way to work out who they 'really are' then they misunderstand the very nature of human social competition.
Group interviews are also insulting to potential employees. A one on one or panel interview tells the potential employee that you've bothered to read their resume and you think they have a shot at the job. You're willing to take the time to meet them personally and see if they're a fit for your company and vice versa. With a one on one interview, you might be nervous, but you at least have a good shot at the position you're interviewing for.
A group interview says that you have no qualms about wasting a potential employee's time by making them jump through socially painful hoops (even the wildest extrovert doesn't want to have to interview in front of what can only be a hostile group of competitors). It says that you don't care enough about the position being filled to take the time to screen resumes properly and conduct face to face interviews. That can't give the potential employee any sense of security about their future job satisfaction.
I've seen some employers defending group interviews as a way to make sure that prospective employees are a good 'culture fit'. This is as balderdash as balderdash gets. Unless, of course, your company culture involves being a meaningless peon, in which case, that's probably a decent argument. Other employers argue that if some candidates are put off by the group interview process, then that's fine because others aren't. They don't seem to realize that the ones who aren't are, by definition, the most desperate for a job. If you want to hire based on desperation, then more power to you, but I sincerely doubt that the best candidate for any given job is the one most willing to have their time wasted in a horribly uncomfortable and likely pointless situation.