Publishing during your PhD should you?

Over at Philosophy Et Cetera Richard has asked for advice in getting the most out of grad school. I made the suggestion that it is never too soon to start publishing, which has prompted a surprisingly contentious discussion of whether you should or shouldn't aim to publish during your PhD.

I thought I would continue that discussion here. Personally I think you ought to be aiming to publish during your PhD.

While there maybe a case to be made that if you are aiming at the top twenty universities perhaps they hire more on potential than on publications. Likewise there may be peculiarities of the system of the country you are in that mean you should save your biggest guns until after you are employed. (For tenure credit for example)

I'd be surprised though if it was the case more generally that publishing before you had finished your PhD really did harm your chances of getting a position. Certainly in my own experiences of job hunting or being involved in job panels, the amount and quality of candidates publications were taken to be very relevant to the question of whether they should be appointed or not. (Although certainly not the only factor)

But I am curious to hear what others think.
So should you try and publish while you are doing your PhD?