Writing code during an interview. Bleh. I always marvel when people think this is a good idea. My response to this idea is this:

If you are going to hire the person to work under constant stress, then by all means go ahead and have them write code in the interview, with people looking on, and use this as a major contributing factor in the hire decision. You will likely know how they perform under stress, that's for sure.

I don't know about you other managers, but I strive to have people code while NOT UNDER STRESS. People under stress do really dumb things. In fact, a very good HR person I know, who is also a therapist, once cited a study that shows when people are under stress they use a small fraction of their intelligence and fall back on primitive behavior (protection of self, fight or flight, etc). Not the best conditions in which to write code.

Now, I think there are some people who will not get stressed when presented with the directive to write code in an interview. They'll be able to do the task OK (or not, depending on their expertise). However, do you really want to select for people that can do this task under these conditions? I think not.

Now, I'll give my 0.02 about interviewing:

I look for 2 things: is this person competent in the area in which they will work and do I think they will fit in? The first part is relatively easy. The second is remarkably difficult and is remarkably ignored. I wish I had a $1 for every time someone suggested hiring the person that had the first part but none of the second.

I have seen brilliant flame outs by really smart people that either couldn't communicate or were impossible to get along with.